<PAGE>   1
                                                                     Exhibit 4.2


                                                                  EXECUTION COPY


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                          PASS THROUGH TRUST AGREEMENT

                            Dated as of July 13, 2000

                                     between

                                PPL MONTANA, LLC,

                                       and

                            THE CHASE MANHATTAN BANK,
                   not in its individual capacity, but solely
                             as Pass Through Trustee

                        Colstrip 2000 Pass Through Trust

                        8.903% Pass Through Certificates

                      COLSTRIP GENERATING UNITS 1, 2 AND 3
                          AND RELATED COMMON FACILITIES




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                                TABLE OF CONTENTS


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SECTION 1.     DEFINITIONS ........................................................      2

      Section 1.1.    Definitions .................................................      2

      Section 1.2.    Compliance Certificates and Opinions ........................      8

      Section 1.3.    Form of Documents Delivered to Pass Through Trustee .........      9

      Section 1.4.    Acts of Holders .............................................      9

      Section 1.5.    Conflict with Trust Indenture Act ...........................     10

SECTION 2.     ACQUISITION OF LESSOR NOTES; ORIGINAL ISSUANCE OF CERTIFICATES .....     10

      Section 2.1.    Issuance of Certificates; Acquisition of Lessor Notes .......     10

      Section 2.2.    Acceptance by Pass Through Trustee ..........................     11

      Section 2.3.    Limitation of Powers ........................................     12

SECTION 3.     THE CERTIFICATES ...................................................     12

      Section 3.1.    Form, Denomination and Execution of Certificates ............     12

      Section 3.2.    Authentication of Certificates ..............................     13

      Section 3.3.    Temporary Certificates ......................................     13

      Section 3.4.    Registration of Transfer and Exchange of Certificates .......     13

      Section 3.5.    Mutilated, Destroyed, Lost or Stolen Certificates ...........     15

      Section 3.6.    Persons Deemed Owners .......................................     16

      Section 3.7.    Cancellation ................................................     16

      Section 3.8.    Limitation of Liability for Payments ........................     16

      Section 3.9.    Book-Entry and Definitive Certificates ......................     16

      Section 3.10.   Form of Certification .......................................     19

SECTION 4.     DISTRIBUTIONS; STATEMENTS TO CERTIFICATEHOLDERS ....................     20

      Section 4.1.    Certificate Account and Special Payments Account ............     20

      Section 4.2.    Distributions from Certificate Account and Special
                      Payments Account ............................................     20

      Section 4.3.    Statements to Certificateholders ............................     22

      Section 4.4.    Investment of Special Payment Moneys ........................     22

SECTION 5.     FINANCIAL STATEMENTS AND OTHER REPORTS .............................     23

SECTION 6.     DEFAULT ............................................................     23
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                                TABLE OF CONTENTS

                                   (CONTINUED)


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      Section 6.1.    Events of Default .............................................   23

      Section 6.2.    Incidents of Sale of Lessor Notes .............................   24

      Section 6.3.    Judicial Proceedings Instituted by Pass Through Trustee .......   25

      Section 6.4.    Control by Certificateholders .................................   25

      Section 6.5.    Waiver of Defaults ............................................   26

      Section 6.6.    Undertaking to Pay Court Costs ................................   27

      Section 6.7.    Right of Certificateholders to Receive Payments Not to
                      Be Impaired ...................................................   27

      Section 6.8.    Certificateholders May Not Bring Suit Except Under
                      Certain Conditions ............................................   27

      Section 6.9.    Remedies Cumulative ...........................................   28

SECTION 7.     THE PASS THROUGH TRUSTEE .............................................   28

      Section 7.1.    Certain Duties and Responsibilities ...........................   28

      Section 7.2.    Notice of Defaults ............................................   29

      Section 7.3.    Certain Rights of Pass Through Trustee ........................   29

      Section 7.4.    Not Responsible for Recitals; Issuance of Certificates ........   31

      Section 7.5.    May Hold Certificates .........................................   31

      Section 7.6.    Money Held in Pass Through Trust ..............................   31

      Section 7.7.    Compensation, Reimbursement and Indemnification ...............   31

      Section 7.8.    Corporate Trustee Required; Eligibility .......................   32

      Section 7.9.    Resignation and Removal: Appointment of Successor .............   32

      Section 7.10.   Acceptance of Appointment by Successor ........................   34

      Section 7.11.   Merger, Conversion, Consolidation or Succession to Business ...   34

      Section 7.12.   Maintenance of Agencies .......................................   34

      Section 7.13.   Money for Certificate Payments to Be Held in Trust ............   35

      Section 7.14.   Registration of Lessor Notes in Pass Through Trustee's Name ...   36

      Section 7.15.   Withholding Taxes; Information Reporting ......................   36

SECTION 8.     CERTIFICATEHOLDERS' LISTS AND REPORTS ................................   37

      Section 8.1.    The Company to Furnish Pass Through Trustee with Names and
                      Addresses of Certificateholder ................................   37
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                                TABLE OF CONTENTS

                                   (CONTINUED)


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      Section 8.2.    Preservation of Information ...................................   37

      Section 8.3.    Reports by the Company ........................................   37

      Section 8.4.    Reports by the Pass Through Trustee ...........................   37

SECTION 9.     SUPPLEMENTAL TRUST AGREEMENTS ........................................   38

      Section 9.1.    Supplemental Trust Agreement Without Consent of
                      Certificateholders ............................................   38

      Section 9.2.    Supplemental Trust Agreements with Consent of
                      Certificateholders ............................................   39

      Section 9.3.    Documents Affecting Immunity or Indemnity .....................   40

      Section 9.4.    Execution of Supplemental Trust Agreements ....................   40

      Section 9.5.    Effect of Supplemental Trust Agreements .......................   40

      Section 9.6.    Reference in Certificates to Supplemental Trust Agreements ....   40

      Section 9.7.    Conformity with Trust Indenture Act ...........................   40

SECTION 10.    AMENDMENTS AND CONSENTS TO LEASE INDENTURES AND OTHER LESSOR NOTE
               DOCUMENTS ............................................................   40

SECTION 11.    TERMINATION OF PASS THROUGH TRUST ....................................   41

      Section 11.1.   Termination of the Pass Through Trust .........................   41

SECTION 12.    MISCELLANEOUS PROVISIONS .............................................   42

      Section 12.1.   Amendments and Waivers ........................................   42

      Section 12.2.   Limitation on Rights of Certificateholders ....................   42

      Section 12.3.   Certificates Nonassessable and Fully Paid .....................   43

      Section 12.4.   Notices .......................................................   43

      Section 12.5.   Successors and Assigns ........................................   43

      Section 12.6.   Business Day ..................................................   44

      Section 12.7.   Governing Law .................................................   44

      Section 12.8.   Severability ..................................................   44

      Section 12.9.   Benefits of Pass Through Trust Agreement ......................   44

      Section 12.10.  Counterparts ..................................................   44

      Section 12.11.  Headings and Table of Contents ................................   44

      Section 12.12.  Further Assurances ............................................   44
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                                TABLE OF CONTENTS

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      Section 12.13.  Effectiveness .................................................   44

      Section 12.14.  Statement of Intent ...........................................   45
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                          PASS THROUGH TRUST AGREEMENT


            This PASS THROUGH TRUST AGREEMENT, dated as of July 13, 2000 (this
"Pass Through Trust Agreement"), with respect to the formation of the Colstrip
2000 Pass Through Trust (the "Pass Through Trust"), between PPL MONTANA, LLC, a
Delaware limited liability company ("PPL Montana" or the "Company"), and THE
CHASE MANHATTAN BANK, a New York corporation, as Pass Through Trustee (the "Pass
Through Trustee").

                              W I T N E S S E T H :

            WHEREAS, the Company, the Pass Through Trustee, and certain other
parties named therein have entered into the four Participation Agreements
referred to on Schedule 1 hereto (collectively, the "Participation Agreements"),
pursuant to which the Company has agreed to (a) sell to each of the Owner
Lessors certain undivided interests in Colstrip Units 1 and 2 and/or Colstrip
Unit 3, and (b) lease from the Owner Lessors such Undivided Interests;

            WHEREAS, PPL Montana will consummate the sale to and lease from the
Owner Lessors of the Undivided Interests on the Closing Date;

            WHEREAS, on the Closing Date, each of the Owner Lessors will enter
into a separate Lease Indenture and issue, on a non-recourse basis, Lessor Notes
thereunder to finance a portion of the purchase price for its Undivided
Interest;

            WHEREAS, subject to the terms and conditions of this Pass Through
Trust Agreement, the Pass Through Trust will purchase the Lessor Notes issued in
connection with the purchase of the Undivided Interests from PPL Montana on the
Closing Date and will hold all such Lessor Notes in trust for the benefit of the
Certificateholders;

            WHEREAS, the Pass Through Trustee, upon the execution and delivery
of this Pass Through Trust Agreement, hereby declares the creation of this Pass
Through Trust for the benefit of the Certificateholders, and the initial
Certificateholders as the grantors of the Pass Through Trust and by their
respective acceptances of the Certificates join in the creation of this Pass
Through Trust with the Pass Through Trustee; and

            WHEREAS, to facilitate the sale of the Lessor Notes to the Pass
Through Trust and the purchase of the Lessor Notes by the Pass Through Trust,
the Company is undertaking to perform certain administrative and ministerial
duties hereunder and is also undertaking to pay the fees and expenses of the
Pass Through Trustee.

            NOW, THEREFORE, in consideration of the foregoing premises, the
mutual agreements herein contained, and of the other good and valuable
consideration the receipt and adequacy of which are hereby acknowledged, the
parties hereto agree as follows:
<PAGE>   7
SECTION 1. DEFINITIONS

      Section 1.1. Definitions.

            (a) Unless the context hereof otherwise requires, capitalized terms
used in this Pass Through Trust Agreement, including those in the recitals, and
not otherwise defined herein shall have the respective meanings set forth in
Appendix A to the applicable Participation Agreement. The general provisions of
Appendix A to each such Participation Agreement shall apply to the terms used in
this Pass Through Trust Agreement and specifically defined herein.

            (b) As used in this Pass Through Trust Agreement, the following
terms shall have the respective meanings assigned thereto as follows:

                  "Act", when used with respect to any Holder, shall have the
            meaning specified in Section 1.4.

                  "Authorized Agent" shall mean any Paying Agent or Registrar.

                  "Book-Entry Certificate" shall mean a beneficial interest in
            the Certificates, ownership and transfers of which shall be made
            through book entries by a Clearing Agency as described in Section
            3.9.

                  "Cedelbank" shall have the meaning specified in Section 3.9.

                  "Certificate" shall mean any one of the certificates executed
            and authenticated by the Pass Through Trustee, substantially in the
            form of Exhibit A hereto.

                  "Certificate Account" shall mean that account or accounts
            created and maintained pursuant to Section 4.1(a).

                  "Certificate Owner" shall mean, when used in Section 3.9, the
            Person for whom a Clearing Agency Participant acts.

                  "Certificate Owner Request" shall mean a request to the Pass
            Through Trustee to receive the reports and other information the
            Company or any other Person is required to furnish to the Pass
            Through Trustee pursuant to the Operative Documents, which request
            certifies that the Person making the request is a Certificateholder
            or Certificate Owner. Any Certificateholder or Certificate Owner
            making a Certificate Owner Request may specify its election to
            receive such information from the Pass Through Trustee on an ongoing
            basis.

                  "Certificateholder" or "Holder" shall mean the Person in whose
            name a Certificate is registered in the Register, except that, when
            used in Section 3.9, such term means the Certificate Owners.

                  "Clearing Agency" shall mean an organization registered as a
            "clearing agency" pursuant to Section 17A of the Exchange Act.


                                       2
<PAGE>   8
                  "Clearing Agency Participant" shall mean a broker, dealer,
            bank, other financial institution or other Person for whom from time
            to time a Clearing Agency effects, directly or indirectly,
            book-entry transfers and pledges of securities deposited with the
            Clearing Agency.

                  "Commission" shall mean the Securities and Exchange
            Commission, as from time to time constituted, created under the
            Exchange Act.

                  "Company" shall have the meaning specified in the Preamble
            hereto.

                  "Consideration" shall have the meaning specified in Section
            2.1.

                  "Corporate Trust Office" shall mean, with respect to the Pass
            Through Trustee, any Lessor Manager and any Lease Indenture Trustee,
            the office of such trustee in the city in which at any particular
            time its corporate trust business shall be administered.

                  "Default" shall mean any event which is or, after notice or
            lapse of time or both would become, an Event of Default.

                  "Definitive Certificates" shall have the meaning specified in
            Section 3.9.

                  "Direction" shall have the meaning specified in Section
            1.4(c).

                  "Distribution Date" shall mean, with respect to distributions
            of Scheduled Payments, each January 2 and July 2 until payment of
            all the Scheduled Payments to be made under the Lessor Notes have
            been made, commencing on January 2, 2001.

                  "DTC" shall mean The Depository Trust Company and any
            successor that is a Clearing Agency.

                  "Euroclear" shall have the meaning specified in Section 3.9.

                  "Event of Default" shall have the meaning specified in Section
            6.1(a).

                  "Exchange Act" shall mean the Securities Exchange Act of 1934,
            as amended.

                  "Exchange Certificate" shall have the meaning specified in
            Section 1.4(f).

                  "Fractional Undivided Interest" shall mean the fractional
            undivided interest in the Pass Through Trust that is evidenced by a
            Certificate.

                  "Holder" shall have the meaning set forth in the definition of
            "Certificateholder".


                                       3
<PAGE>   9
                  "Institutional Accredited Investor" shall mean an
            institutional "accredited investor", as such term is defined in Rule
            501(a)(1), (2), (3) or (7) under the Securities Act.

                  "Lease" shall mean a Facility Lease Agreement between an Owner
            Lessor, as the lessor, and the Company, as the lessee, entered into
            pursuant to a Participation Agreement, as such Lease may be amended
            or supplemented in accordance with its terms. The term "Lease"
            refers to any one or all of such Leases, as the context requires.

                  "Lease Event of Default" shall mean any Lease Event of Default
            (as such term is defined in a Lease).

                  "Lease Indenture" shall mean (i) an Indenture of Trust,
            Mortgage and Security Agreement between an Owner Lessor and a Lease
            Indenture Trustee, entered into pursuant to a Participation
            Agreement, as the same may be amended or supplemented in accordance
            with its terms and (ii) any Indenture of Trust, Mortgage and
            Security Agreement, or analogous document, between the Company and a
            Lease Indenture Trustee, entered into in connection with the
            assumption by the Company of the indebtedness evidenced by any
            Lessor Note, as the same may be amended or supplemented in
            accordance with its terms. The term "Lease Indenture" refers to any
            one or all of such Lease Indentures, as the context requires.

                  "Lease Indenture Default" shall mean any event which is, or
            after notice or lapse of time or both would become, a Lease
            Indenture Event of Default.

                  "Lease Indenture Event of Default" shall mean any Lease
            Indenture Event of Default (as such term is defined in a Lease
            Indenture).

                  "Lease Indenture Trustee" shall mean a bank or trust company
            acting as indenture trustee under a Lease Indenture, and any
            successor to such Lease Indenture Trustee as such trustee. The term
            "Lease Indenture Trustee" refers to any one or all of such Lease
            Indenture Trustees, as the context requires.

                  "Lease Transaction" shall mean a sale leaseback transaction in
            respect of an Undivided Interest between the Company and an Owner
            Lessor that is financed in part by the issuance of Lessor Notes to
            the Pass Through Trust, as contemplated by a Participation Agreement
            and the agreements and instruments referred to therein.

                  "Lessor Manager" shall mean a bank or trust company acting as
            manager of an Owner Lessor, not in its individual capacity, but
            solely as manager of such Owner Lessor pursuant to an operating
            agreement with an Owner Participant, and any successor to such
            Lessor Manager as such manager. The term "Lessor Manager" refers to
            any one or all of such Lessor Managers, as the context requires.


                                       4
<PAGE>   10
                  "Lessor Note" shall mean any one of the Notes (as defined in
            each Lease Indenture) issued under a Lease Indenture, including the
            Lessor Note (as so defined) issued under a Lease Indenture in
            replacement or substitution therefor, held by the Pass Through
            Trustee.

                  "Lessor Note Documents" shall mean, with respect to any Lessor
            Note, the applicable Lease Indenture, Participation Agreement and
            the Lease entered into pursuant to such Participation Agreement.

                  "Letter of Representations" shall mean the agreement among the
            Company, the Pass Through Trustee and the initial Clearing Agency.

                  "Opinion of Counsel" shall mean an opinion in writing signed
            by legal counsel, who may be counsel designated by the Company, an
            Owner Lessor or a Lease Indenture Trustee, whether or not such
            counsel is an employee of any of them, and who shall be acceptable
            to the Pass Through Trustee in its reasonable discretion.

                  "Outstanding" shall mean, when used with respect to
            Certificates, as of the date of determination, and subject to
            Section 1.4(c), all Certificates theretofore authenticated and
            delivered under this Pass Through Trust Agreement, except:

                  (i) Certificates theretofore canceled by the Registrar or
            delivered to the Pass Through Trustee or the Registrar for
            cancellation;

                  (ii) Certificates for which money in the full amount thereof
            has been theretofore deposited with the Pass Through Trustee or any
            Paying Agent in trust for the holders of such Certificates as
            provided in Section 4.1 pending distribution of such money to the
            Certificateholders pursuant to the final distribution payment to be
            made pursuant to Section 11.1; and

                  (iii) Certificates in exchange for or in lieu of which other
            Certificates have been authenticated and delivered pursuant to this
            Pass Through Trust Agreement.

                  "Owner Lessor" shall mean a limited liability company
            established in connection with a Lease Transaction, pursuant to an
            operating agreement between an Owner Participant and a Lessor
            Manager, for the purpose of issuing Lessor Notes, purchasing an
            Undivided Interest and entering into the related Lease, all as
            provided in a Participation Agreement, and any successors and
            assigns permitted by the applicable Participation Agreement. The
            term "Owner Lessor" refers to any one or all of such Owner Lessors,
            as the context requires.

                  "Owner Participant" shall mean the owner of an interest in an
            Owner Lessor, identified as an "Owner Participant" in a
            Participation Agreement, and any successors and assigns permitted by
            the applicable Participation Agreement. The term "Owner Participant"
            refers to any one or all of such Owner Participants, as the context
            requires.


                                       5
<PAGE>   11
                  "Participation Agreement" shall mean a Participation Agreement
            among the Company, an Owner Participant, an Owner Lessor, a Lessor
            Manager, a Lease Indenture Trustee and the Pass Through Trustee,
            providing for a Lease Transaction. The term "Participation
            Agreement" refers to any one or all of such Participation
            Agreements, as the context requires. Each Participation Agreement
            that provides for a Lease Transaction which is to be financed with
            Lessor Notes purchased by the Pass Through Trustee hereunder,
            together with the identities of the Owner Lessor, the Lessor
            Manager, the Owner Participant and the Lease Indenture Trustee that
            will be parties thereto, is identified on Schedule 1 hereto.

                  "Pass Through Trust" shall mean the trust created by this Pass
            Through Trust Agreement, the estate of which consists of the Trust
            Property.

                  "Pass Through Trustee" shall mean the institution executing
            this Pass Through Trust Agreement as Pass Through Trustee, or its
            successor in interest, and any successor trustee appointed as
            provided herein.

                  "Paying Agent" shall mean the paying agent maintained and
            appointed pursuant to Section 7.12.

                  "Permanent Regulation S Global Certificate" shall have the
            meaning specified in Section 3.9.

                  "Permitted Government Investment" shall mean the obligations
            of the United States of America for the payment of which the full
            faith and credit of the United States of America is pledged,
            maturing in not more than 60 days or such lesser time as is
            necessary for payment of any Special Payments on a Special
            Distribution Date.

                  "Record Date" shall mean (i) for Scheduled Payments to be
            distributed on any Distribution Date, other than the final
            distribution, the day (whether or not a Business Day) which is
            fifteen days preceding such Distribution Date, and (ii) for Special
            Payments to be distributed on any Special Distribution Date, other
            than the final distribution, the day (whether or not a Business Day)
            which is fifteen days preceding such Special Distribution Date.

                  "Register" and "Registrar" shall mean the register maintained
            and the registrar appointed pursuant to Sections 3.4 and 7.12.

                  "Registration Rights Agreement" shall mean the Registration
            Rights Agreement, dated as of July 20, 2000 among the Initial
            Purchasers and the Company.

                  "Regulation S Global Certificate" shall have the meaning
            specified in Section 3.9.

                  "Request" shall mean a request by the Company, any Owner
            Lessor, or any Lease Indenture Trustee setting forth the subject
            matter of the request


                                       6
<PAGE>   12
            accompanied by an Officer's Certificate and an Opinion of Counsel as
            provided in Section 1.2.

                  "Responsible Officer" shall mean, when used with respect to
            any Person, any officer having responsibility for the administration
            of the Operative Documents, including the chairman or vice-chairman
            of the board of directors or trustees, the chairman or vice-chairman
            of the executive or standing committee of the board of directors or
            trustees, the president, the chairman of the committee on trust
            matters, any vice-president, any second vice-president, the
            secretary, any assistant secretary, the treasurer, any assistant
            treasurer, any trust officer or assistant trust officer, any other
            officer of such Person customarily performing functions similar to
            those performed by any of the above designated officers and also,
            with respect to a particular matter, any other officer of such
            Person to whom such matter is referred because of such officer's
            knowledge of and familiarity with the particular subject.

                  "Restricted Certificate" shall have the meaning specified in
            Section 3.1.

                  "Restricted Global Certificate" shall have the meaning
            specified in Section 3.9.

                  "Scheduled Payment" shall mean, with respect to a Distribution
            Date, any payment (other than a Special Payment) of principal and
            interest on a Lessor Note, due from an Owner Lessor, which payment
            represents the payment of a regularly scheduled installment of
            principal then due on such Lessor Note, or the payment of regularly
            scheduled interest accrued on such Lessor Note.

                  "Securities Act" shall mean the Securities Act of 1933, as
            amended.

                  "Special Distribution Date" shall mean (i) with respect to the
            prepayment of any Lessor Notes, the day on which such prepayment is
            scheduled to occur pursuant to the terms of the relevant Lease
            Indenture, and (ii) with respect to any Special Payment relating to
            a Lessor Note other than as described in clause (i) of the
            definition of Special Payment, the earliest second day of a month
            for which it is practicable for the Pass Through Trustee to give
            notice pursuant to Section 4.2(c).

                  "Special Payment" shall mean (i) any payment of principal,
            premium, if any, and interest on a Lessor Note resulting from the
            prepayment of such Lessor Note pursuant to the applicable provisions
            of the relevant Lease Indenture, (ii) any payment of principal and
            interest (including any interest accruing upon default) on, or any
            other amount in respect of, such Lessor Note upon a Lease Indenture
            Event of Default in respect thereof or upon the exercise of remedies
            under the Lease Indenture relating to such Lessor Note, (iii) any
            Special Payment referred to in clause (i) of this definition or any
            Scheduled Payment which is not in fact paid within five days of the
            Special Distribution Date or Distribution Date


                                       7
<PAGE>   13
            applicable thereto, or (iv) any proceeds from the sale of any Lessor
            Note by the Pass Through Trustee pursuant to Section 6 hereof.

                  "Special Payments Account" shall mean the account or accounts
            created and maintained pursuant to Section 4.1(b).

                  "Temporary Regulation S Global Certificate" shall have the
            meaning specified in Section 3.9.

                  "Transfer Date" shall mean the closing date of the public
            offering of the Certificates.

                  "Trust Indenture Act" shall mean the Trust Indenture Act of
            1939, as amended and as in force on the date on which this Pass
            Through Trust Agreement was executed and delivered, except as
            provided in Section 9.7; provided, however, that in the event the
            Trust Indenture Act of 1939 is amended after such date, "Trust
            Indenture Act" shall mean, to the extent required by any such
            amendment, the Trust Indenture Act of 1939 as so amended.

                  "Trust Property" shall mean the Lessor Notes held as the
            property of the Pass Through Trust created hereby and all monies at
            any time paid thereon and all monies due and to become due
            thereunder, funds from time to time deposited in the Certificate
            Account and the Special Payments Account and any proceeds from the
            sale by the Pass Through Trustee pursuant to Section 6 hereof of any
            Lessor Note.

                  "Undivided Interest" shall mean, with respect to a specific
            Participation Agreement, the Undivided Interest conveyed to the
            Owner Lessor pursuant to such Participation Agreement to the extent
            the Unit Interests that make up the Undivided Interest are then
            subject to a Lease.

      Section 1.2. Compliance Certificates and Opinions.

            (a) Upon any application or request by the Company, any Owner Lessor
or any Lease Indenture Trustee to the Pass Through Trustee to take any action
under any provision of this Pass Through Trust Agreement, the Company, such
Owner Lessor or such Lease Indenture Trustee, as the case may be, shall furnish
to the Pass Through Trustee an Officer's Certificate stating that, in the
opinion of the signers, all conditions precedent, if any, provided for in this
Pass Through Trust Agreement relating to the proposed action have been complied
with and an Opinion of Counsel stating that in the opinion of such counsel all
such conditions precedent, if any, have been complied with, except that in the
case of any such application or request as to which the furnishing of such
documents is specifically required by any provision of this Pass Through Trust
Agreement relating to such particular application or request, no additional
certificate or opinion need be furnished.

            (b) Every certificate or opinion with respect to compliance with a
condition or covenant provided for in this Pass Through Trust Agreement shall
include:


                                       8
<PAGE>   14
            (1) a statement that each individual signing such certificate or
      opinion has read such covenant or condition and the definitions herein
      relating thereto;

            (2) a brief statement as to the nature and scope of the examination
      or investigation upon which the statements or opinions contained in such
      certificate or opinion are based;

            (3) a statement that, in the opinion of each such individual, he has
      made such examination or investigation as is necessary to enable him to
      express an informed opinion as to whether or not such covenant or
      condition has been complied with; and

            (4) a statement as to whether, in the opinion of each such
      individual, such condition or covenant has been complied with.

      Section 1.3. Form of Documents Delivered to Pass Through Trustee.

            (a) In any case where several matters are required to be certified
by, or covered by an opinion of, any specified Person, it is not necessary that
all such matters be certified by, or covered by the opinion of, only one such
Person, or that they be so certified or covered by only one document, but one
such Person may certify or give an opinion with respect to some matters and one
or more other such Persons as to other matters and any such Person may certify
or give an opinion as to such matters in one or several documents.

            (b) Any Opinion of Counsel stated to be based on the opinion of
other counsel shall be accompanied by a copy of such other opinion.

            (c) Where any Person is required to make, give or execute two or
more applications, requests, consents, certificates, statements, opinions or
other instruments under this Pass Through Trust Agreement, they may, but need
not, be consolidated and form one instrument.

      Section 1.4. Acts of Holders.

            (a) Any direction, consent, waiver or other action provided by this
Pass Through Trust Agreement to be given or taken by Holders may be embodied in
and evidenced by one or more instruments of substantially similar tenor signed
by such Holders in person or by an agent or agents duly appointed in writing;
and, except as herein otherwise expressly provided, such action shall become
effective when such instrument or instruments are delivered to the Pass Through
Trustee and, where it is hereby expressly required, to the Company, any Owner
Lessor or any Lease Indenture Trustee. Such instrument or instruments (and the
action embodied therein and evidenced thereby) are herein sometimes referred to
as the "Act" of the Holders signing such instrument or instruments. Proof of
execution of any such instrument or of a writing appointing any such agent shall
be sufficient for any purpose of this Pass Through Trust Agreement and (subject
to Section 7.1) conclusive in favor of the Pass Through Trustee, the Company,
any Owner Lessor and any Lease Indenture Trustee, if made in the manner provided
in this Section.


                                       9
<PAGE>   15
            (b) The fact and date of the execution by any Person of any such
instrument or writing may be proved in any reasonable manner which the Pass
Through Trustee deems sufficient.

            (c) In determining whether the Holders of the requisite Fractional
Undivided Interests of Certificates Outstanding have given any direction,
consent or waiver (a "Direction"), under this Pass Through Trust Agreement,
Certificates owned by the Company, the Owner Lessor, the Owner Participant or
any Affiliate of any such Person shall be disregarded and deemed not to be
Outstanding under this Pass Through Trust Agreement for purposes of any such
determination. In determining whether the Pass Through Trustee shall be
protected in relying upon any such Direction, only Certificates which the Pass
Through Trustee knows to be so owned shall be so disregarded. Notwithstanding
the foregoing, (i) if any such Person owns 100% of the Certificates Outstanding,
such Certificates shall not be so disregarded as aforesaid, and (ii) if any
amount of Certificates so owned by any such Person have been pledged in good
faith, such Certificates shall not be disregarded as aforesaid if the pledgee
establishes to the satisfaction of the Pass Through Trustee the pledgee's right
so to act with respect to such Certificates and that the pledgee is not one of
the Company, the Owner Lessor, the Owner Participant or any Affiliate of any
such Person.

            (d) Any Act by the Holder of any Certificate shall bind the Holder
of every Certificate issued upon the transfer thereof or in exchange therefor or
in lieu thereof, whether or not notation of such Act is made upon such
Certificate.

            (e) Except as otherwise provided in Section 1.4(c), Certificates
owned by or pledged to any Person shall have an equal and proportionate benefit
under the provisions of this Pass Through Trust Agreement, without preference,
priority or distinction as among all of the Certificates.

            (f) Notwithstanding anything herein to the contrary, the
Certificates and any Certificates that are Exchange Certificates (as defined in
the Registration Rights Agreement) will vote and consent together on all matters
as one class and will not have the right to vote or consent as a separate class
on any matter.

            Section 1.5. Conflict with Trust Indenture Act. If any provision
hereof limits, qualifies or conflicts with a provision of the Trust Indenture
Act that is required or deemed under such Act to be a part of and govern this
Pass Through Trust Agreement, such required or deemed provision shall, so long
as the Certificates shall be subject to the Trust Indenture Act, control. If any
provision of this Pass Through Trust Agreement modifies or excludes any
provision of the Trust Indenture Act that may be so modified or excluded, the
latter provision shall be deemed to apply to this Indenture as so modified or to
be excluded, as the case may be.

SECTION 2. ACQUISITION OF LESSOR NOTES; ORIGINAL ISSUANCE OF CERTIFICATES

      Section 2.1. Issuance of Certificates; Acquisition of Lessor Notes.

            (a) The Pass Through Trustee, at or promptly following the execution
and delivery of this Pass Through Trust Agreement, shall also execute and
deliver each of the


                                       10
<PAGE>   16
Participation Agreements, in the form delivered to the Pass Through Trustee on
or prior to the date of the execution and delivery hereof. Upon delivery of an
authentication order by PPL Montana and the satisfaction of the closing
conditions with respect to the Lessor Notes in Section 4 of the Participation
Agreements, the Pass Through Trustee shall execute, deliver and authenticate, on
behalf of the Pass Through Trust, Certificates equaling in the aggregate the
total principal amount of the Lessor Notes deposited into the Pass Through Trust
on the Transfer Date. The Certificates so executed, delivered and authenticated
on the Transfer Date shall evidence the entire ownership of the Pass Through
Trust. The Pass Through Trust shall issue such Certificates on the Transfer
Date, in authorized denominations and in such Fractional Undivided Interests, so
as to result in the receipt of consideration (the "Consideration") in an amount
equal to the aggregate principal amount of such Lessor Notes referred to in the
second preceding sentence. The Pass Through Trust shall purchase Lessor Notes on
the Transfer Date at an aggregate purchase price equal to the amount of the
Consideration so received. Except as provided in Sections 3.4 and 3.5 hereof,
the Pass Through Trustee shall not execute or deliver Certificates in excess of
the aggregate amount specified in this paragraph.

            (b) Company Assumption of Lessor Notes. If the Company shall assume
the obligations of an Owner Lessor under any Lessor Note pursuant to any Lease
Indenture, the Pass Through Trustee shall, upon its receipt of written
instructions from the Company, surrender the Lessor Notes issued pursuant to
such Lease Indenture to the Lease Indenture Trustee in exchange for new Lessor
Notes of the same aggregate outstanding principal amount as the Lessor Notes so
surrendered, bearing interest at the same rate, and having the same maturity and
amortization schedule, and otherwise of similar tenor, issued under such Lease
Indenture and any new Lease Indenture entered into by the Company and the Lease
Indenture Trustee in connection with such assumption, and thereafter each
reference to such Lessor Notes in this Pass Through Trust Agreement shall be
deemed to mean a reference to such new Lessor Notes.

            (c) Authentication. Any authentication order delivered by PPL
Montana hereunder shall be signed by one of its authorized signatories and shall
specify the amount and maturity of the Certificates to be authenticated and the
date on which the original issue of Certificates is to be authenticated. The
Pass Through Trustee may appoint an authenticating agent to authenticate the
Certificates. Unless limited by the terms of such appointment, an authenticating
agent may authenticate the Certificates whenever the Pass Through Trustee may do
so. Each reference in this Pass Through Trust Agreement to authentication by the
Pass Through Trustee includes authentication by such agent. An authenticating
agent has the same rights as any Registrar, Paying Agent or agent for service of
notices and demands.

      Section 2.2. Acceptance by Pass Through Trustee. The Pass Through Trustee,
upon the execution and delivery of this Pass Through Trust Agreement,
acknowledges on behalf of the Pass Through Trust its acceptance of all right,
title, and interest in and to the Lessor Notes acquired pursuant to Section 2.1
hereof and declares that the Pass Through Trustee holds and will hold such
right, title, and interest, together with all other property constituting the
Trust Property, for the benefit of all present and future Certificateholders,
upon the trusts herein set forth. By its payment for and acceptance of each
Certificate issued to it hereunder, each initial Certificateholder as grantor of
the Pass Through Trust thereby joins in the creation and declaration of the Pass
Through Trust. The Pass Through Trustee shall be under no duty or obligation to
inspect, review or examine the Lessor Notes to determine that they are genuine,


                                       11
<PAGE>   17
valid, binding, enforceable or appropriate for the represented purpose or that
they are other than what they purport to be on their face.

      Section 2.3. Limitation of Powers. The Pass Through Trust is constituted
solely for the purpose of making the investment in the Lessor Notes, and, except
as set forth herein, the Pass Through Trustee is not authorized or empowered to
acquire any other investments or engage in any other activities and, in
particular, the Pass Through Trustee is not authorized or empowered to do
anything that would cause the Pass Through Trust to fail to qualify as a pass
through entity for federal income tax purposes (including, as subject to this
restriction, acquiring any Undivided Interest or any portion thereof by bidding
the Lessor Notes or otherwise, or taking any action with respect to any
Undivided Interest or any portion thereof once acquired).

SECTION 3. THE CERTIFICATES

      Section 3.1. Form, Denomination and Execution of Certificates. The
Certificates shall be issued in registered form without coupons and shall be
substantially in the form attached hereto as Exhibit A, with such omissions,
variations and insertions as are permitted by this Pass Through Trust Agreement,
and may have such letters, numbers or other marks of identification and such
legends or endorsements printed, lithographed or engraved thereon, as may be
required to comply with the rules of any securities exchange on which such
Certificates may be listed or to conform to any usage in respect thereof, or as
may, consistently herewith, be prescribed by the Pass Through Trustee or by the
officer executing such Certificates, such determination by said officer to be
evidenced by his signing the Certificates.

            Except as provided in Section 3.9, definitive Certificates shall be
printed, lithographed or engraved or produced by any combination of these
methods or may be produced in any other manner permitted by the rules of any
securities exchange on which the Certificates may be listed, all as determined
by the officer executing such Certificates, as evidenced by his execution of
such Certificates.

            During the period beginning on the Closing Date and ending on the
date two years from the Closing Date, all Certificates issued on the Closing
Date, and all Certificates issued upon registration of transfer of, or in
exchange for, such Certificates, shall be "Restricted Certificates" and shall be
subject to the restrictions on transfer provided in the legend set forth on the
face of the form of certificate in Exhibit A; provided, however, that the term
"Restricted Certificates" shall not include Certificates as to which such
restrictions on transfer have been terminated in accordance with Section 3.4.
All Restricted Certificates shall bear the legend set forth on the face of the
Certificate in Exhibit A. Certificates which are not Restricted Certificates
shall not bear such legend.

            The Certificates shall be issued in minimum denominations of
$100,000 or integral multiples of $1,000 in excess thereof.

            The Certificates shall be executed on behalf of the Pass Through
Trust by manual or facsimile signature of a Responsible Officer of the Pass
Through Trustee. Certificates bearing the manual or facsimile signature of an
individual who was, at the time when such signature was affixed, authorized to
sign on behalf of the Pass Through Trustee shall be valid and binding


                                       12
<PAGE>   18
obligations of the Pass Through Trust, notwithstanding that such individual has
ceased to be so authorized prior to the authentication and delivery of such
Certificates or did not hold such office at the date of such Certificates. No
Certificate shall be entitled to any benefit under this Pass Through Trust
Agreement, or be valid for any purpose unless there appears on such Certificate
a certificate of authentication substantially in the form set forth in Exhibit B
hereto executed by the Pass Through Trustee by manual signature, and such
certificate of authentication upon any Certificate shall be conclusive evidence,
and the only evidence, that such Certificate has been duly authenticated and
delivered hereunder. All Certificates shall be dated the date of their
authentication.

      Section 3.2. Authentication of Certificates. Upon delivery of an
authentication order by PPL Montana, the Pass Through Trustee shall cause to be
delivered Certificates duly authenticated by the Pass Through Trustee, in
authorized denominations equaling in the aggregate the aggregate principal
amount set forth in the authentication order evidencing the entire ownership of
the Pass Through Trust.

      Section 3.3. Temporary Certificates. Pending the preparation of definitive
Certificates, the Pass Through Trustee may execute, authenticate and deliver
temporary Certificates which are printed, lithographed, typewritten, or
otherwise produced, in any denomination, containing substantially the same terms
and provisions as set forth in Exhibit A, except for such appropriate
insertions, omissions, substitutions and other variations relating to their
temporary nature as the officer executing such temporary Certificates may
determine, as evidenced by his or her execution of such temporary Certificates.

            If temporary Certificates are issued, the Company will cause
definitive Certificates to be prepared without unreasonable delay. After the
preparation of definitive Certificates, the temporary Certificates shall be
exchangeable for definitive Certificates upon surrender of the temporary
Certificates at the Corporate Trust Office of the Pass Through Trustee, or at
the office or agency of the Pass Through Trustee maintained in accordance with
Section 7.12, without charge to the Holder. Upon surrender for cancellation of
any one or more temporary Certificates, the Pass Through Trustee shall execute,
authenticate and deliver in exchange therefor definitive Certificates of
authorized denominations of a like aggregate Fractional Undivided Interest.
Until so exchanged, such temporary Certificates shall in all respects be
entitled to the same benefits under this Pass Through Trust Agreement as
definitive Certificates.

      Section 3.4. Registration of Transfer and Exchange of Certificates.

            (a) The Pass Through Trustee shall cause to be kept, at the office
or agency to be maintained by it in accordance with the provisions of Section
7.12, a register (the "Register") in which, subject to the provisions of this
Section 3.4 and the Certificates, the Pass Through Trustee shall provide for the
registration of Certificates and of transfers and exchanges of Certificates as
herein provided. The Pass Through Trustee shall initially be the registrar (the
"Registrar") for the purpose of registering Certificates and transfers and
exchanges of Certificates as herein provided.


                                       13
<PAGE>   19
            (b) Every Restricted Certificate shall be subject to the
restrictions on transfer provided in the legend required to be set forth on the
face of each Restricted Certificate pursuant to Section 3.1, and the Holder of
each Restricted Certificate, by such Holder's acceptance thereof, agrees to be
bound by such restrictions on transfer. Whenever any Restricted Certificate is
presented or surrendered for registration of transfer or for exchange for a
Certificate registered in a name other than that of the Holder, such Restricted
Certificate must be accompanied by a certificate in substantially the form set
forth in Exhibit C hereto, dated the date of such surrender and signed by the
Holder of such Restricted Certificate, or such Holder's attorney duly authorized
in writing, as to compliance with such restrictions on transfer. Neither the
Pass Through Trustee nor any Registrar shall be required to accept for such
registration of transfer or exchange any Restricted Certificate not so
accompanied by a properly completed certificate. Notwithstanding the preceding
two sentences, a properly completed certificate shall not be required in
connection with any transfer of any Restricted Certificate through the
facilities of DTC or any other United States securities clearance and settlement
organization; provided, that such transfer does not require a change in the name
(other than to another nominee of DTC or such other securities clearance and
settlement organization) in which such Restricted Certificate is then
registered.

      Whenever any Restricted Certificate is proposed to be transferred by a
Holder to an Institutional Accredited Investor, the Pass Through Trustee shall
have received from such Institutional Accredited Investor, prior to such
transfer, a signed letter substantially in the form of Exhibit D relating to
certain representations and agreements regarding restrictions on transfer of
such Restricted Certificate. In addition, if such Restricted Certificate
evidences a Fractional Undivided Interest of less than $100,000, the
Institutional Accredited Investor must, prior to such transfer, furnish to the
Registrar an Opinion of Counsel to confirm that such transfer is being made
pursuant to an exemption from, or in a transaction not subject to, the
registration requirements of the Securities Act.

            The restrictions imposed by this Section 3.4 and Section 3.1 upon
the transferability of any particular Restricted Certificate shall cease and
terminate if and when such Restricted Certificate has been (i) sold pursuant to
an effective registration statement under the Securities Act, (ii) exchanged for
Exchange Certificates that are freely tradable under the Securities Act, or
(iii) transferred pursuant to Rule 144 under the Securities Act (or any
successor provision thereto), unless the Holder thereof is an affiliate of the
Company within the meaning of Rule 144 (or such successor provision). Any
Restricted Certificate as to which such restrictions on transfer shall have
expired in accordance with their terms or shall have terminated may, upon
surrender of such Restricted Certificate for exchange to the Pass Through
Trustee or any Registrar in accordance with the provisions of this Section 3.4
(accompanied, in the event that such restrictions on transfer have terminated by
reason of a transfer pursuant to Rule 144 or any successor provision, by an
Opinion of Counsel having substantial experience in practice under the
Securities Act and otherwise reasonably acceptable to the Company, addressed to
the Company and the Pass Through Trustee and in form acceptable to the Company,
to the effect that the transfer of such Restricted Certificate has been made in
compliance with Rule 144 or such successor provision), be exchanged for a new
Certificate, of authorized denominations of a like aggregate Fractional
Undivided Interest, which shall not bear the restrictive legend required by
Section 3.1. The Company shall promptly inform the Pass Through Trustee in
writing of the effective date of any registration statement registering the
Certificates under the Securities Act.


                                       14
<PAGE>   20
The Pass Through Trustee shall not be liable for any action taken or omitted to
be taken by it in good faith in accordance with the aforementioned Opinion of
Counsel or registration statement.

            (c) Upon surrender for registration of transfer of any Certificate
that is not a Restricted Certificate at the Corporate Trust Office or such other
office or agency, the Pass Through Trustee shall execute, authenticate and
deliver, in the name of the designated transferee or transferees, one or more
new Certificates, in authorized denominations of a like aggregate Fractional
Undivided Interest.

            (d) At the option of a Certificateholder, Certificates may be
exchanged for other Certificates, in authorized denominations and of a like
aggregate Fractional Undivided Interest, upon surrender of the Certificates to
be exchanged at any such office or agency; provided, that a Restricted
Certificate may only be exchanged for another Restricted Certificate, until such
restrictions on such Restricted Certificate shall cease and terminate in
accordance with the terms of this Section 3.4. Whenever any Certificates are so
surrendered for exchange, the Pass Through Trustee shall execute, authenticate
and deliver the Certificates that the Certificateholder making the exchange is
entitled to receive. Every Certificate presented or surrendered for registration
of transfer or exchange shall be duly endorsed or accompanied by a written
instrument of transfer in form satisfactory to the Company and the Pass Through
Trustee and the Registrar duly executed by the Certificateholder thereof or its
attorney duly authorized in writing.

            (e) No service charge shall be made to a Certificateholder for any
registration of transfer or exchange of Certificates, but the Pass Through
Trustee shall require payment of a sum sufficient to cover any tax or charge
that may be imposed in connection with any transfer or exchange of Certificates.

            (f) All Certificates surrendered for registration of transfer and
exchange shall be canceled and disposed of in accordance with the usual
practices of the Pass Through Trustee.

      Section 3.5. Mutilated, Destroyed, Lost or Stolen Certificates. If any
mutilated Certificate is surrendered to the Registrar, or the Registrar receives
evidence to its satisfaction of the destruction, loss or theft of any
Certificate and in the case of such destruction, loss or theft, there is
delivered to the Registrar, the Pass Through Trustee, the Company and each Owner
Lessor such security, indemnity or bond as may be required by them to protect
each of them and the Pass Through Trust from any loss that any of them may
suffer if a Certificate is replaced, then, in the absence of notice to the
Registrar or the Pass Through Trustee that such Certificate has been acquired by
a bona fide purchaser, the Pass Through Trustee, on behalf of the Pass Through
Trust, shall execute, authenticate and deliver, in exchange for or in lieu of
any such mutilated, destroyed, lost or stolen Certificate, a new Certificate of
like Fractional Undivided Interest with the same final Distribution Date. In
connection with the issuance of any new Certificate under this Section 3.5, the
Pass Through Trustee shall require the payment of a sum sufficient to cover any
tax or other charge that may be imposed in relation thereto and any other
expenses (including the fees and expenses of the Pass Through Trustee and the
Registrar) connected therewith. Any duplicate Certificate issued pursuant to
this Section 3.5 shall constitute conclusive evidence of the appropriate
Fractional Undivided Interest in the Pass


                                       15
<PAGE>   21
Through Trust, as if originally issued, whether or not the lost, stolen or
destroyed Certificate shall be found at any time.

      Section 3.6. Persons Deemed Owners. Prior to due presentation of a
Certificate for registration of transfer, the Pass Through Trustee, the Company,
each Owner Lessor, the Registrar and any Paying Agent may treat the person in
whose name any Certificate is registered as the owner of such Certificate for
the purpose of receiving distributions pursuant to Section 4.2 and for all other
purposes whatsoever, and neither the Pass Through Trustee, the Company, each
Owner Lessor, the Registrar nor any Paying Agent shall be affected by any notice
to the contrary.

      Section 3.7. Cancellation. All Certificates surrendered for payment,
transfer or exchange shall, if surrendered to any Person a party hereto other
than the Registrar, be delivered by such Person to the Registrar for
cancellation. No Certificates shall be authenticated in lieu of or in exchange
for any Certificates canceled as provided in this Section 3.7, except as
expressly permitted by this Pass Through Trust Agreement. All canceled
Certificates held by the Registrar shall be disposed of in accordance with the
usual practice of the Pass Through Trustee and, if destroyed, a certification of
their destruction shall be delivered to the Pass Through Trustee.

      Section 3.8. Limitation of Liability for Payments. All payments or
distributions made to Certificateholders under this Pass Through Trust Agreement
shall be made only from the Trust Property and only to the extent that the Pass
Through Trustee shall have received sufficient income or proceeds from the Trust
Property to make such payments in accordance with the terms of Section 4 of this
Pass Through Trust Agreement. Each Holder of a Certificate, by its acceptance of
such Certificate, agrees that it will look solely to the income and proceeds
from the Trust Property to the extent available for distribution to the Holder
thereof as provided in this Pass Through Trust Agreement. Nothing in this Pass
Through Trust Agreement shall be construed as an agreement, or otherwise
creating an obligation, of (a) the Company, the Pass Through Company or the Pass
Through Trustee to pay any of the principal, premium, if any, or interest due
from time to time under the Lessor Notes, or (b) the Company, the Pass Through
Company or the Pass Through Trustee to pay any amount due from time to time in
respect of the Certificates. The liability of each Owner Lessor under the
applicable Lessor Notes shall be limited as set forth therein and in the
relevant Lease Indenture.

      Section 3.9. Book-Entry and Definitive Certificates.

            (a) Except for Certificates issued to Institutional Accredited
Investors which must be issued in the form of definitive, fully registered
Certificates ("Definitive Certificates"), the Certificates may be issued in the
form of one or more typewritten Certificates representing the Book-Entry
Certificates to be delivered to DTC, the initial Clearing Agency, by, or on
behalf of, the Pass Through Trustee. In such case, the Certificates delivered to
DTC shall initially be registered on the Register in the name of Cede & Co., the
nominee of the initial Clearing Agency, and no Certificate Owner will receive a
definitive certificate representing such Certificate Owner's interest in the
Certificates, except as provided above and in subsection (d) below. As to the
Book-Entry Certificates, unless and until Definitive Certificates have been
issued pursuant to subsection (d) below:


                                       16
<PAGE>   22
                  (i) the provisions of this Section 3.9 shall be in full force
            and effect;

                  (ii) the Company, each Owner Lessor, the Paying Agent, the
            Registrar and the Pass Through Trustee may deal with the Clearing
            Agency for all purposes (including the making of distributions on
            the Certificates) as the authorized representative of the
            Certificate Owners;

                  (iii) to the extent that the provisions of this Section 3.9
            conflict with any other provisions of this Pass Through Trust
            Agreement (other than the provisions of any supplemental agreement
            amending this Section 3.9 as permitted by this Pass Through Trust
            Agreement), the provisions of this Section 3.9 shall control;

                  (iv) the rights of Certificate Owners shall be exercised only
            through the Clearing Agency and shall be limited to those
            established by law and agreements between such Certificate Owners
            and the Clearing Agency Participants; and until Definitive
            Certificates are issued pursuant to subsection (d) below, the
            Clearing Agency will make book-entry transfers among the Clearing
            Agency Participants and receive and transmit distributions of
            principal and interest and premium, if any, on the Certificates to
            such Clearing Agency Participants; and

                  (v) whenever this Pass Through Trust Agreement requires or
            permits actions to be taken based upon instructions or directions of
            Certificateholders holding Certificates evidencing a specified
            percentage of the Fractional Undivided Interests in the Pass Through
            Trust, the Clearing Agency shall be deemed to represent such
            percentage only to the extent that it has received instructions to
            such effect from Certificate Owners and/or Clearing Agency
            Participants owning or representing, respectively, such required
            percentage of the beneficial interest in Certificates and has
            delivered such instructions to the Pass Through Trustee. The Pass
            Through Trustee shall have no obligation to determine (and shall
            incur no liability in connection with any determination of) whether
            the Clearing Agency has in fact received any such instructions.

            (b) With respect to Book-Entry Certificates, whenever notice or
other communication to the Certificateholders is required under this Pass
Through Trust Agreement, unless and until Definitive Certificates shall have
been issued pursuant to subsection (d) below, the Pass Through Trustee shall
give all such notices and communications specified herein to be given to
Certificateholders to the Clearing Agency and/or the Clearing Agency
Participants (and, upon receipt of a valid Certificate Owner Request, to the
Certificateholder or Certificate Owner making such request), and shall make
available additional copies as reasonably requested by such Clearing Agency
Participants.

            (c) Unless and until Definitive Certificates are issued pursuant to
subsection (d) below, on the Record Date prior to each applicable Distribution
Date and Special


                                       17
<PAGE>   23
Distribution Date, the Pass Through Trustee will request from the Clearing
Agency a "Securities Position Listing" setting forth the names of all Clearing
Agency Participants reflected on the Clearing Agency's books as holding
interests in the Certificates on such Record Date. The Pass Through Trustee
shall mail to each such Clearing Agency Participant the statements described in
Section 4.3 hereof.

            (d) If with respect to the Certificates (i) the Company advises the
Pass Through Trustee in writing that the Clearing Agency is no longer willing or
able to properly discharge its responsibilities and the Company is unable to
locate a qualified successor, (ii) the Company (or, following the occurrence of
a Lease Event of Default, the relevant Owner Lessor) at its option, advises the
Pass Through Trustee in writing that it elects to terminate the book-entry
system through the Clearing Agency or (iii) after the occurrence of an Event of
Default, Certificate Owners of Book-Entry Certificates evidencing Fractional
Undivided Interests aggregating not less than a majority in interest in the Pass
Through Trust, by Act of said Certificate Owners delivered to the Company and
the Pass Through Trustee, advise the Company, the relevant Owner Lessor, the
Pass Through Trustee and the Clearing Agency through the Clearing Agency
Participants in writing that the continuation of a book-entry system through the
Clearing Agency is no longer in the best interests of the Certificate Owners,
then the Pass Through Trustee shall notify all Certificate Owners, through the
Clearing Agency, of the occurrence of any such event and of the availability of
Definitive Certificates. Upon surrender to the Pass Through Trustee of all the
Certificates held by the Clearing Agency, accompanied by registration
instructions from the Clearing Agency for registration of Definitive
Certificates in the names of Certificate Owners, the Pass Through Trust shall
issue and deliver the Definitive Certificates in accordance with the
instructions of the Clearing Agency. None of the Company, the Owner Lessors, the
Registrar, the Paying Agent or the Pass Through Trustee shall be liable for any
delay in delivery of such instructions and may conclusively rely on, and shall
be protected in relying on, such registration instructions. Upon the issuance of
Definitive Certificates, the Pass Through Trustee shall recognize the Person in
whose name the Definitive Certificates are registered in the Register as
Certificateholder hereunder. Neither the Company nor the Pass Through Trustee
shall be liable if the Company is unable to locate a qualified successor
Clearing Agency.

            (e) The Certificates sold in offshore transactions in reliance on
Regulation S under the Securities Act will be represented initially by a single,
temporary Book-Entry Certificate, in definitive, fully registered form without
interest coupons (the "Temporary Regulation S Global Certificate") and will be
deposited with the Pass Through Trustee as custodian for DTC and registered in
the name of a nominee of DTC for the accounts of Morgan Guaranty Trust Company
of New York, Brussels Office, as operator of the Euroclear System ("Euroclear"),
and Cedelbank ("Cedelbank"). Each Temporary Regulation S Global Certificate will
be exchangeable for a single, permanent Book-Entry Certificate (the "Permanent
Regulation S Global Certificate," and together with the Temporary Regulation S
Global Certificate, the "Regulation S Global Certificate") on or after 40 days
after the later of the commencement of the offering of the Certificates and the
Closing Date upon certification that the beneficial interests in such Book-Entry
Certificate are owned by persons who are not U.S. persons as defined in
Regulation S. Prior to the expiration of such 40-day period, beneficial
interests in the Temporary Regulation S Global Certificate may be held only
through Euroclear or Cedelbank, and any resale or other transfer of such
interests to U.S. persons shall not be


                                       18
<PAGE>   24
permitted during such period unless such resale or transfer is made pursuant to
Rule 144A or Regulation S under the Securities Act and in accordance with the
certification requirements specified in Section 3.9(f) below. The aggregate
original principal amount of the Regulation S Global Certificate may from time
to time be increased or decreased by adjustments made on the records of the Pass
Through Trustee, as custodian for DTC, in connection with a corresponding
decrease or increase in the aggregate original principal amount of a Definitive
Certificate or the Restricted Global Certificate, as hereinafter provided.

            (f) The Certificates sold in reliance on Rule 144A under the
Securities Act will be represented by a single, permanent Book-Entry
Certificate, in definitive, fully registered form without interest coupons (the
"Restricted Global Certificate"), which will be deposited with the Pass Through
Trustee as custodian for DTC and registered in the name of a nominee of DTC.
Prior to the 40th day after the later of the commencement of the offering of the
Certificates and the Closing Date, a beneficial interest in the Temporary
Regulation S Global Certificate may be transferred to a person who takes
delivery in the form of an interest in the Restricted Global Certificate only
upon receipt by the Pass Through Trustee of a written certification from the
transferor (in the form of Exhibit C hereto) to the effect that such transfer is
being made to a person who the transferor reasonably believes is a "qualified
institutional buyer" within the meaning of Rule 144A in a transaction meeting
the requirements of Rule 144A and in accordance with any applicable securities
laws of any state of the United States or any other jurisdiction. Beneficial
interests in the Restricted Global Certificate may be transferred to a person
who takes delivery in the form of an interest in the Regulation S Global
Certificate whether before, on or after such 40th day, only upon receipt by the
Pass Through Trustee of a written certification (in the form of Exhibit C
hereto) to the effect that such transfer is being made in accordance with
Regulation S under the Securities Act and, if such transfer occurs prior to such
40th day, the interest will be held immediately thereafter only through
Euroclear or Cedelbank. The aggregate initial principal amount of the Restricted
Global Certificate may from time to time be increased or decreased by
adjustments made on the records of the Pass Through Trustee, as custodian for
DTC, in connection with a corresponding decrease or increase in the aggregate
initial principal amount of a Definitive Certificate or a Regulation S Global
Certificate, as hereinafter provided.

            (g) Any beneficial interest in one of the Book-Entry Certificates
that is transferred to a person who takes delivery in the form of an interest in
another Book-Entry Certificate will, upon transfer, cease to be an interest in
such first Book-Entry Certificate and become an interest in such other
Book-Entry Certificate and, accordingly, will thereafter be subject to all
transfer restrictions, if any, and other procedures applicable to beneficial
interests in such other Book-Entry Certificate for so long as it remains such an
interest. Upon the transfer of Definitive Certificates to a qualified
institutional buyer or in accordance with Regulation S, such Definitive
Certificates will be exchanged for an interest in a Book-Entry Certificate.

            (h) The Company and the Pass Through Trustee, if necessary, shall
each enter into the Letter of Representations with respect to the Certificates
and fulfill its responsibilities thereunder.

      Section 3.10. Form of Certification. In connection with any certification
contemplated by Section 3.4, relating to compliance with certain restrictions
relating to transfers of Restricted


                                       19
<PAGE>   25
Certificates, such certification shall be provided substantially in the form of
Exhibit C hereto, with only such changes as shall be reasonably approved by the
Company and reasonably acceptable to the Pass Through Trustee.

SECTION 4. DISTRIBUTIONS; STATEMENTS TO CERTIFICATEHOLDERS

      Section 4.1. Certificate Account and Special Payments Account.

            (a) The Pass Through Trust shall establish and maintain on behalf of
the Certificateholders the Certificate Account with the Pass Through Trustee as
one or more non-interest bearing accounts. The Pass Through Trustee shall hold
the Certificate Account in trust for the benefit of the Certificateholders, and
shall make or permit withdrawals therefrom only as provided in this Pass Through
Trust Agreement. On each day when a Scheduled Payment is made and identified as
such under a Lease Indenture to the Pass Through Trust, as holder of the Lessor
Notes issued under such Lease Indenture, the Pass Through Trustee upon receipt
shall immediately deposit the aggregate amount of such Scheduled Payment in the
Certificate Account.

            (b) The Pass Through Trust shall establish and maintain on behalf of
the Certificateholders the Special Payments Account with the Pass Through
Trustee as one or more accounts, which shall be non-interest bearing except as
provided in Section 4.4. The Pass Through Trustee shall hold the Special
Payments Account in trust for the benefit of the Certificateholders, and shall
make or permit withdrawals therefrom only as provided in this Pass Through Trust
Agreement. On each day when a Special Payment is made and identified as such
under a Lease Indenture to the Pass Through Trustee, as holder of the Lessor
Notes issued under such Lease Indenture, the Pass Through Trustee upon receipt
shall immediately deposit the aggregate amounts of such Special Payments in the
Special Payments Account.

            (c) The Pass Through Trustee shall present to the applicable Lease
Indenture Trustee each Lessor Note on the date of its stated final maturity, or
in the case of any Lessor Note which is to be prepaid in whole pursuant to the
Lease Indenture, on the applicable prepayment date under such Lease Indenture.

      Section 4.2. Distributions from Certificate Account and Special Payments
Account.

            (a) On each Distribution Date if the Pass Through Trustee receives
payment of the Scheduled Payments due on any Lessor Notes on such date by 11:00
a.m., New York time, on such date, the Pass Through Trustee shall distribute out
of the Certificate Account the entire amount deposited therein pursuant to
Section 4.1(a). If a Scheduled Payment is received by the Pass Through Trustee
after 11:00 a.m., New York time, on a Distribution Date, such payment shall be
distributed on the next Business Day. If a Scheduled Payment is not received by
the Pass Through Trustee on a Distribution Date but is received prior to the
time such payment would become a Special Payment, such payment shall be
distributed (i) on the date received, if received by 11:00 a.m., New York time,
on such date or (ii) on the next Business Day, if received after 11:00 a.m., New
York time, on such date. There shall be so distributed to each Certificateholder
of record on the Record Date with respect to such Distribution Date (other than
as provided in Section 11.1 concerning the final distribution) (i) if (A) DTC is
the Certificateholder of record,


                                       20
<PAGE>   26
or (B) a Certificateholder holds a Certificate or Certificates in an aggregate
amount greater than $10,000,000 or (C) a Certificateholder holds a Certificate
or Certificates in an aggregate amount greater than $1,000,000 and so requests
to the Pass Through Trustee, by wire transfer in immediately available funds to
an account maintained by such Certificateholder with a bank, or (ii) if none of
the above apply, by check mailed to such Certificateholder at the address
appearing in the Register, such Certificateholder's pro rata share (based on the
aggregate Fractional Undivided Interest held by such Certificateholder) of the
aggregate amount in the Certificate Account.

            (b) On each Special Distribution Date with respect to any Special
Payment if the Pass Through Trustee receives the Special Payments due on the
required date by 11:00 a.m., New York time, on such date, the Pass Through
Trustee shall distribute out of the Special Payments Account the entire amount
deposited therein with respect to such Special Payment pursuant to this Section
4.1(b). If a Special Payment is received by the Pass Through Trustee after 11:00
a.m., New York time, on a Special Distribution Date, such payment shall be
distributed on the next Business Day. If a Special Payment is not received by
the Pass Through Trustee on a Special Distribution Date, such payment shall be
distributed (i) on the date received, if received by 11:00 a.m., New York time,
on such date or (ii) on the next Business Day, if received after 11:00 a.m., New
York time, on such date. There shall be so distributed to each Certificateholder
of record on the Record Date with respect to such Special Distribution Date
(other than as provided in Section 11.1 concerning the final distribution) (i)
if (A) DTC is the Certificateholder of record, or (B) a Certificateholder holds
a Certificate or Certificates in an aggregate amount greater than $10,000,000 or
(C) a Certificateholder holds a Certificate or Certificates in an aggregate
amount greater than $1,000,000 and so requests to the Pass Through Trustee, by
wire transfer in immediately available funds to an account maintained by the
Certificateholder with a bank, or (ii) if none of the above apply, by check
mailed to such Certificateholder at the address appearing in the Register, such
Certificateholder's pro rata share (based on the aggregate Fractional Undivided
Interest held by such Certificateholder) of the aggregate amount in the Special
Payments Account on account of such Special Payment.

            (c) The Pass Through Trustee shall, at the expense of the Company,
cause notice of each Special Payment to be mailed to (i) each Certificateholder,
at the address of such Certificateholder as it appears in the Register and (ii)
any Certificate Owner who has made a valid Certificate Owner Request, at the
address specified in such Certificate Owner Request. In the event of prepayment
of any Lessor Notes, such notice shall be mailed not less than 20 days prior to
the date any such Special Payment is scheduled to be distributed. In the case of
any other Special Payments, such notice shall be mailed as soon as practicable
after the Pass Through Trustee has confirmed that it has received funds for such
Special Payment. Notices mailed by the Pass Through Trustee shall set forth:

                  (i) the Special Distribution Date and the Record Date therefor
            (except as otherwise provided in Section 11.1);

                  (ii) the amount of the Special Payment per $1,000 of face
            amount of Certificates and the amount thereof constituting
            principal, premium, if any, and interest;


                                       21
<PAGE>   27
                  (iii) the reason for the Special Payment; and

                  (iv) if the Special Distribution Date is the same date as a
            Distribution Date, the total amount to be received on such date per
            $1,000 of face amount of Certificates.

If the amount of premium payable upon the prepayment of a Lessor Note has not
been calculated at the time that the Pass Through Trustee mails notice of a
Special Payment, it shall be sufficient if the notice sets forth the other
amounts to be distributed and states that any premium received will also be
distributed. If a Distribution Date or Special Distribution Date is not a
Business Day, distribution shall be made on the immediately following Business
Day.

      Section 4.3. Statements to Certificateholders.

            (a) On each Distribution Date and Special Distribution Date, the
Pass Through Trustee will include with each distribution to Certificateholders a
statement, giving effect to such distribution to be made on such date, setting
forth the following information (per a $1,000 face amount Certificate):

                  (i) the amount of such distribution allocable to principal and
            the amount allocable to premium if any; and

                  (ii) the amount of such distribution allocable to interest.

            (b) Within a reasonable period of time after the end of each
calendar year but not later than the latest date permitted by law, the Pass
Through Trustee shall furnish (i) to each Person who at any time during such
calendar year was a Certificateholder of record and (ii) to any Person who at
any time during such calendar year was a Certificate Owner who has made a valid
Certificate Owner Request and provided the Pass Through Trustee with such
pertinent information as the Pass Through Trustee shall reasonably request, a
statement containing the sum of the amounts determined pursuant to clauses
(a)(i) and (a)(ii) with respect to the Pass Through Trust for such calendar year
or, in the event such Person was a Certificateholder of record or Certificate
Owner during a portion of such calendar year, for the applicable portion of such
year, and such other items as are readily available to the Pass Through Trustee
and which a Certificateholder or Certificate Owner shall reasonably request as
necessary for the purpose of such Certificateholder's or Certificate Owner's
preparation of its Federal income tax returns.

      Section 4.4. Investment of Special Payment Moneys. Any money received by
the Pass Through Trustee pursuant to Section 4.1(b) representing a Special
Payment which is not to be promptly distributed shall, to the extent
practicable, be invested in Permitted Government Investments by the Pass Through
Trustee pending distribution of such Special Payment pursuant to Section 4.2.
Any investment made pursuant to this Section 4.4 shall be in such Permitted
Government Investments having maturities not later than the date that such
moneys are required to be paid to make the payment required under Section 4.2 on
the applicable Special Distribution Date and the Pass Through Trustee shall hold
any such Permitted Government Investments until maturity. The Pass Through
Trustee shall have no liability with respect to any investment made pursuant to
this Section 4.4, other than by reason of the willful misconduct or negligence
of the


                                       22
<PAGE>   28
Pass Through Trustee. All income and earnings from such investments shall be
distributed on such Special Distribution Date as part of such Special Payment.

SECTION 5. FINANCIAL STATEMENTS AND OTHER REPORTS

      For so long as any Certificates remain Outstanding, the Company shall
furnish:

            (a) to Certificateholders, Certificate Owners and prospective
investors, upon their request, the information required to be delivered pursuant
to Rule 144A(d)(4) under the Securities Act so long as the Certificates are not
freely transferable under the Securities Act; and

            (b) to the Pass Through Trustee, who in turn shall provide such
information, upon a Certificate Owner Request, to Certificateholders and
Certificate Owners:

                  (i) within 60 days following the end of each of the first
            three fiscal quarters of the Company during each fiscal year, a copy
            of Form 10-Q (or any successor form) filed by the Company with the
            Commission for such fiscal quarter, or if the Company is not then
            subject to the reporting requirements of the Exchange Act, unaudited
            consolidated quarterly financial statements for the Company for such
            fiscal quarter in the form required by Section 5.3(b) of the
            Participation Agreements;

                  (ii) within 120 days following the end of the fiscal year of
            the Company, a copy of the Form 10-K (or any successor form) filed
            by the Company with the Commission for such fiscal year, or, if the
            Company is not then subject to the reporting requirements of the
            Exchange Act, audited consolidated annual financial statements in
            the form required by Section 5.3(a) of the Participation Agreements;
            and

                  (iii) within 20 days after the occurrence thereof, (A) a copy
            of any current report on Form 8-K (or any successor form) filed by
            the Company with the Commission, if any, and (B) notice of the
            following events (1) a Change of Control; (2) any litigation or
            claim against the Company, its Core Subsidiaries or the Colstrip
            Project which could reasonably be expected to have a Material
            Adverse Effect; (3) the appointment of a receiver over the Company
            or the confirmation of a plan of reorganization or liquidation for
            the Company; or (4) the resignation or dismissal of the independent
            accountants engaged by the Company.

SECTION 6. DEFAULT

      Section 6.1. Events of Default.

            (a) If any Lease Indenture Event of Default under any Lease
Indenture (an "Event of Default") shall occur and be continuing, then, and in
each and every case, so long as such Lease Indenture Event of Default shall be
continuing, the Pass Through Trustee may vote all of the Lessor Notes issued
under such Lease Indenture held in the Pass Through Trust, and upon the
Direction of the Holders of Certificates evidencing Fractional Undivided
Interests aggregating not less than a majority in interest of the Fractional
Undivided Interests evidenced


                                       23
<PAGE>   29
by all Certificates at the time Outstanding (determined as provided in Section
1.4(c)), the Pass Through Trustee shall vote a corresponding majority of such
Lessor Notes, in favor of directing the Lease Indenture Trustee to declare the
unpaid principal amount of such Lessor Notes then outstanding and accrued
interest thereon to be due and payable under, and to the extent permitted by and
in accordance with, the provisions of such Lease Indenture.

            In addition, after an Event of Default shall have occurred and be
continuing, the Pass Through Trustee may in its discretion, and upon the
Direction of the Holders of Certificates evidencing Fractional Undivided
Interests aggregating not less than a majority in interest of the Fractional
Undivided Interests evidenced by all Certificates at the time Outstanding
(determined as provided in Section 1.4(c)) shall, by such officer or agent as it
may appoint, sell, convey, transfer and deliver all or a portion of such Lessor
Note or Lessor Notes issued under the Lease Indenture with respect to which the
Event of Default has occurred, without recourse to or warranty by the Pass
Through Trustee or any Certificateholders to any Person. In any such case, the
Pass Through Trustee shall sell, assign, contract to sell or otherwise dispose
of and deliver such Lessor Note or Lessor Notes in one or more parcels at public
or private sale or sales, at any location or locations at the option of the Pass
Through Trustee, all upon such terms and conditions as it may reasonably deem
advisable and at such prices as it may reasonably deem advisable, for cash. The
Pass Through Trustee shall give notice to the Company and the applicable Owner
Lessor promptly after any such sale.

      Section 6.2. Incidents of Sale of Lessor Notes. Upon any sale of all or
any part of the Lessor Notes made either under the power of sale given under
this Pass Through Trust Agreement or otherwise for the enforcement of this Pass
Through Trust Agreement, the following shall be applicable:

            (1) Certificateholders and Pass Through Trustee May Purchase Lessor
      Notes. Any Certificateholder, the Pass Through Trustee in its individual
      or any other capacity or any other Person may bid for and purchase any of
      the Lessor Notes and, upon compliance with the terms of sale, may hold,
      retain, possess and dispose of such Lessor Notes in their or its or his
      own absolute right without further accountability.

            (2) Receipt of Pass Through Trustee Shall Discharge Purchaser. The
      receipt of immediately available funds by the Pass Through Trustee or the
      officer or agent appointed by the Pass Through Trustee shall be a
      sufficient discharge to any purchaser for his purchase money, and, after
      paying such purchase money and receiving such receipt, such purchaser or
      his personal representative or assigns shall not be obliged to see to the
      application of such purchase money, or be in any way answerable for any
      loss, misapplication or non-application thereof.

            (3) Application of Moneys Received upon Sale. Any moneys collected
      by the Pass Through Trustee, upon any sale made either under the power of
      sale given by this Pass Through Trust Agreement or otherwise for the
      enforcement of this Pass Through Trust Agreement, shall be applied as
      provided in Section 4.2.


                                       24
<PAGE>   30
      Section 6.3. Judicial Proceedings Instituted by Pass Through Trustee.

            (a) Pass Through Trustee May Bring Suit. If there shall be a failure
to make payment of the principal of, premium, if any, or interest on any Lessor
Note, or if there shall be any failure to pay Rent (as defined in a Lease) under
the Lease related to any Lessor Note when due and payable, then the Pass Through
Trustee, in its own name, and as trustee of an express trust, as holder of such
Lessor Notes shall be, to the extent permitted by and in accordance with the
terms of the Lessor Note Documents, entitled and empowered (but not obligated)
to institute any suits, actions or proceedings at law, in equity or otherwise,
for the collection of the sums so due and unpaid on such Lessor Notes or under
such Lease and may prosecute any such claim or proceeding to judgment or final
decree with respect to the whole amount of any such sums so due and unpaid;
subject, however, to the limitations of liability set forth in the Lessor Notes
and the Lessor Note Documents.

            (b) Pass Through Trustee May File Proofs of Claim; Appointment of
Pass Through Trustee as Attorney-in-Fact in Judicial Proceedings. The Pass
Through Trustee in its own name, or as trustee of an express trust, or as
attorney-in-fact for the Certificateholders, or in any one or more of such
capacities (irrespective of whether distributions on the Certificates shall then
be due and payable, or the payment of the principal on the Lessor Notes shall
then be due and payable, as therein expressed or by declaration or otherwise and
irrespective of whether the Pass Through Trustee shall have made any demand to
the applicable Lease Indenture Trustee for the payment of overdue principal,
premium (if any) or interest on the Lessor Notes), shall, subject to the terms
of the Lessor Note Documents, be entitled and empowered to file such proofs of
claim and other papers or documents as may be necessary or advisable in order to
have the claims of the Pass Through Trustee and of the Certificateholders
allowed in any receivership, insolvency, bankruptcy, liquidation, readjustment,
reorganization or any other judicial proceedings relative to the Company or the
applicable Owner Lessor, any Lessor Manager or any Owner Participant, or their
respective creditors or property. Subject to the terms of the Lessor Note
Documents, any receiver, assignee, trustee, liquidator or sequestrator (or
similar official) in any such judicial proceeding is hereby authorized by each
Certificateholder to make payments in respect of such claim to the Pass Through
Trustee, and in the event that the Pass Through Trustee shall consent to the
making of such payments directly to the Certificateholders, to pay to the Pass
Through Trustee any amount due to it for the reasonable compensation, expenses,
disbursements and advances of the Pass Through Trustee, its agents and counsel
and any other amounts due the Pass Through Trustee under Section 7.7. Subject to
Section 6.4, nothing contained in this Pass Through Trust Agreement shall be
deemed to give to the Pass Through Trustee any right to accept or consent to any
plan of reorganization or otherwise by action of any character in any such
proceeding to waive or change in any way any right of any Certificateholder.

      Section 6.4. Control by Certificateholders. The Holders of Certificates
evidencing Fractional Undivided Interests aggregating not less than a majority
in interest of the Fractional Undivided Interests evidenced by all Certificates
at the time Outstanding (determined as provided in Section 1.4(c)) shall have
the right to direct the time, method and place of conducting any proceeding for
any remedy available to the Pass Through Trustee, or exercising any trust or
power conferred upon the Pass Through Trustee, under this Pass Through Trust
Agreement, including any right of the Pass Through Trustee as holder of the
Lessor Notes, provided that:


                                       25
<PAGE>   31
            (1) such Direction shall not be in conflict with any rule of law or
      with this Pass Through Trust Agreement and would not involve the Pass
      Through Trustee in personal liability or expense;

            (2) the Pass Through Trustee shall not determine that the action so
      directed would expose it to personal liability or be unjustly prejudicial
      to the Certificateholders not taking part in such direction;

            (3) the Pass Through Trustee may take any other action deemed proper
      by the Pass Through Trustee which is not inconsistent with such Direction;

            (4) such Holders shall have offered to the Pass Through Trustee
      security or indemnity against the costs, expenses or liabilities which may
      be incurred thereby; and

            (5) if a Lease Indenture Event of Default shall have occurred and be
      continuing, such Direction shall not obligate the Pass Through Trustee to
      vote more than a corresponding majority of the related Lessor Notes held
      by the Pass Through Trust in favor of directing any action by the Lease
      Indenture Trustee with respect to such Lease Indenture Event of Default.

      Section 6.5. Waiver of Defaults. The Holders of Certificates evidencing
Fractional Undivided Interests aggregating not less than a majority in interest
of the Fractional Undivided Interests evidenced by all Certificates at the time
Outstanding (determined as provided in Section 1.4(c)) may on behalf of the
Certificateholders of all the Certificates waive any Default hereunder and its
consequences or may instruct the Pass Through Trustee to waive any default under
a Lease Indenture and its consequences, except:

            (1) a default in the deposit of any Scheduled Payment or Special
      Payment under Section 4.1 or in the distribution of any payment under
      Section 4.2 on the Certificates; or

            (2) a default in the payment of the principal of, premium, if any,
      or interest on any Lessor Notes; or

            (3) a default in respect of a covenant or provision hereof which
      under Section 9 hereof cannot be modified or amended without the consent
      of the Holder of each Outstanding Certificate affected.

            Upon any such waiver, such Default shall cease to exist with respect
to this Pass Through Trust Agreement, and any Event of Default arising therefrom
shall be deemed to have been cured for every purpose of this Pass Through Trust
Agreement and any direction given by the Pass Through Trustee on behalf of such
Holders to the applicable Lease Indenture Trustee shall be annulled with respect
thereto; but no such waiver shall extend to any subsequent or other Default,
Event of Default or impair any right consequent thereon. Upon any such waiver
with respect to a Default under a Lease Indenture, the Pass Through Trustee
shall vote a corresponding majority of the Lessor Notes issued under such Lease
Indenture to waive the corresponding Lease Indenture Default or Lease Indenture
Event of Default.


                                       26
<PAGE>   32
            With respect to consents, approvals, waivers and authorizations
which under the terms of Section 9 of a Lease Indenture may be given by the
applicable Lease Indenture Trustee without the necessity of the consent of any
of the holders of Lessor Notes issued with respect to such Lease Indenture, no
consent, approval, waiver or authorization shall be required hereunder on the
part of the Pass Through Trustee or the Certificateholders.

      Section 6.6. Undertaking to Pay Court Costs. All parties to this Pass
Through Trust Agreement, and each Certificateholder by his acceptance of a
Certificate, shall be deemed to have agreed that any court may in its discretion
require, in any suit, action or proceeding for the enforcement of any right or
remedy under this Pass Through Trust Agreement, or in any suit, action or
proceeding against the Pass Through Trustee for any action taken or omitted by
it as Pass Through Trustee hereunder, the filing by any party litigant in such
suit, action or proceeding of an undertaking to pay the costs of such suit,
action or proceeding, and that such court may, in its discretion, assess
reasonable costs, including reasonable attorneys' fees, against any party
litigant in such suit, action or proceeding, having due regard to the merits and
good faith of the claims or defenses made by such party litigant; provided,
however, that the provisions of this Section 6.6 shall not apply to (a) any
suit, action or proceeding instituted by any Holder, or group of Holders,
holding in the aggregate Certificates evidencing Fractional Undivided Interests
aggregating more than 10% of the Pass Through Trust, (b) any suit, action or
proceeding instituted by any Certificateholder for the enforcement of the
distribution of payments pursuant to Section 4.2 hereof on or after the
respective due dates expressed herein or (c) any suit, action or proceeding
instituted by the Pass Through Trustee.

      Section 6.7. Right of Certificateholders to Receive Payments Not to Be
Impaired. Anything in this Pass Through Trust Agreement to the contrary
notwithstanding, but subject to Section 3.8 hereof, the right of any
Certificateholder to receive distributions of payments required pursuant to
Section 4.2 hereof on the Certificates when due, or to institute suit for the
enforcement of any such payment on or after the applicable Distribution Date or
Special Distribution Date, shall not be impaired or affected without the consent
of such Certificateholder.

      Section 6.8. Certificateholders May Not Bring Suit Except Under Certain
Conditions. A Certificateholder shall not have the right to institute any suit,
action or proceeding at law or in equity or otherwise with respect to this Pass
Through Trust Agreement, for the appointment of a receiver or for the
enforcement of any other remedy under this Pass Through Trust Agreement, unless:

            (1) such Certificateholder previously shall have given written
      notice to the Pass Through Trustee of a continuing Event of Default;

            (2) the Holders of Certificates evidencing Fractional Undivided
      Interests aggregating not less than a majority in interest of the
      Fractional Undivided Interests evidenced by all Certificates at the time
      Outstanding (determined as provided in Section 1.4(c)) shall have
      requested the Pass Through Trustee in writing to institute such suit,
      action or proceeding and shall have offered to the Pass Through Trustee
      indemnity as provided in Section 7.3(e);


                                       27
<PAGE>   33
            (3) the Pass Through Trustee shall have refused or neglected to
      institute any such suit, action or proceeding for 60 days after receipt of
      such notice, request and offer of indemnity; and

            (4) no Direction inconsistent with such written request has been
      given to the Pass Through Trustee during such 60-day period by the Holders
      of Certificates evidencing Fractional Undivided Interests aggregating not
      less than a majority in interest of the Fractional Undivided Interests
      evidenced by all Certificates at the time Outstanding (determined as
      provided in Section 1.4(c)).

            It is understood and intended that no one or more of the
Certificateholders shall have any right in any manner whatever hereunder or
under the Certificates to (i) surrender, impair, waive, affect, disturb or
prejudice any property in the Trust Property or the lien of any Lease Indenture
on any property subject thereto, or the rights of the Certificateholders or the
holders of the Lessor Notes, (ii) obtain or seek to obtain priority over or
preference to any other such Holder, or (iii) enforce any right under this Pass
Through Trust Agreement, except in the manner herein provided and for the equal,
ratable and common benefit of all the Certificateholders subject to the
provisions of this Pass Through Trust Agreement.

      Section 6.9. Remedies Cumulative. Every remedy given hereunder to the Pass
Through Trustee or to any of the Certificateholders shall not be exclusive of
any other remedy or remedies, and every such remedy shall be cumulative and in
addition to every other remedy given hereunder or now or hereafter given by
statute, law, equity or otherwise.

SECTION 7. THE PASS THROUGH TRUSTEE

      Section 7.1. Certain Duties and Responsibilities.

            (a) Prior to an Event of Default of which a Responsible Officer of
the Pass Through Trustee has actual knowledge:

            (1) the Pass Through Trustee shall not be liable except for the
      performance of such duties as are specifically set out in this Pass
      Through Trust Agreement; and

            (2) the Pass Through Trustee may conclusively rely, as to the truth
      of the statements and the correctness of the opinions expressed therein,
      in the absence of bad faith on the part of the Pass Through Trustee, upon
      Officer's Certificates or Opinions of Counsel conforming to the
      requirements of this Pass Through Trust Agreement;

but the Pass Through Trustee shall, at any time that the Certificates shall be
subject to the Trust Indenture Act, examine the evidence furnished to it
pursuant to Section 314 of the Trust Indenture Act to determine whether or not
such evidence conforms to the requirements of this Pass Through Trust Agreement;
provided, however, that the Pass Through Trustee shall not be responsible for
the accuracy or content of such evidence.

            (b) In case an Event of Default has occurred and is continuing, the
Pass Through Trustee shall exercise each of the rights and powers vested in it
by this Pass Through


                                       28
<PAGE>   34
Trust Agreement, and use the same degree of care and skill in their exercise, as
a prudent person would exercise or use under the circumstances in the conduct of
his own affairs.

            (c) No provision of this Pass Through Trust Agreement shall be
construed to relieve the Pass Through Trustee from liability for its own
negligent action, its own negligent failure to act, or its own willful
misconduct, except that:

            (1) this paragraph (c) shall not be construed to limit the effect of
      paragraph (a) of this Section 7.1;

            (2) the Pass Through Trustee shall not be liable in its individual
      capacity for any error of judgment made in good faith by a Responsible
      Officer of the Pass Through Trustee, unless it shall be proved that the
      Pass Through Trustee was negligent in ascertaining the pertinent facts;
      and

            (3) the Pass Through Trustee shall not be liable with respect to any
      action taken or omitted to be taken by it in good faith in accordance with
      the Direction of the Holders of Certificates evidencing Fractional
      Undivided Interests aggregating not less than a majority in interest of
      the Fractional Undivided Interests evidenced by all Certificates at the
      time Outstanding (determined as provided in Section 1.4(c)) (A) relating
      to the time, method and place of conducting any proceeding for any remedy
      available to the Pass Through Trustee, or (B) exercising any trust or
      power conferred upon the Pass Through Trustee, under this Pass Through
      Trust Agreement.

            (d) Whether or not herein expressly so provided, every provision of
this Pass Through Trust Agreement relating to the conduct or affecting the
liability of or affording protection to the Pass Through Trustee shall be
subject to the provisions of this Section 7.1.

      Section 7.2. Notice of Defaults. The Pass Through Trustee shall give to
the Certificateholders, at any time that the Certificates shall be subject to
the Trust Indenture Act, in the manner and to the extent required by Section
313(c) of the Trust Indenture Act, and to the Company, the applicable Owner
Lessor and the applicable Lease Indenture Trustee in accordance with Section
12.4, notice of all Defaults actually known to a Responsible Officer of the Pass
Through Trustee within 90 days after the occurrence thereof; provided, however,
that, except in the case of a Default in the payment of the principal of,
premium, if any, or interest on any Lessor Note, the Pass Through Trustee shall
be protected in withholding such notice if and so long as the board of
directors, the executive committee or a trust committee of directors or
Responsible Officers of the Pass Through Trustee in good faith determine that
the withholding of such notice is in the interests of the Certificateholders.

      Section 7.3. Certain Rights of Pass Through Trustee. Except as otherwise
provided in Section 7.1:

            (a) the Pass Through Trustee may rely and shall be protected in
acting or refraining from acting in reliance upon any Act, Direction,
resolution, certificate, statement, instrument, opinion, report, notice,
request, direction, consent, order, bond, debenture or other paper or document
believed by it to be genuine and to have been signed or presented by the proper
party or parties;

                                       29
<PAGE>   35
            (b) any request or direction of the Company, any Owner Lessor or any
Lease Indenture Trustee mentioned herein shall be sufficiently evidenced by a
Request;

            (c) whenever in the administration of this Pass Through Trust
Agreement the Pass Through Trustee shall deem it desirable that a matter be
proved or established prior to taking, suffering or omitting any action
hereunder, the Pass Through Trustee (unless other evidence be herein
specifically prescribed) may, in the absence of bad faith on its part, rely upon
an Officer's Certificate of the Company, the applicable Owner Lessor or the
applicable Lease Indenture Trustee;

            (d) the Pass Through Trustee may consult with counsel and the advice
of such counsel or any Opinion of Counsel shall be full and complete
authorization and protection in respect of any action taken, suffered or omitted
by it hereunder in good faith and in reliance thereon;

            (e) the Pass Through Trustee shall be under no obligation to
exercise any of the rights or powers vested in it by this Pass Through Trust
Agreement at the request or direction of any of the Certificateholders pursuant
to this Pass Through Trust Agreement, unless such Certificateholders shall have
offered to the Pass Through Trustee reasonable security or indemnity against the
cost, expenses and liabilities which might be incurred by it in compliance with
such request or direction;

            (f) the Pass Through Trustee shall not be bound to make any
investigation into the facts or matters stated in any Act, Direction,
resolution, certificate, statement, instrument, opinion, report, notice,
request, direction, consent, order, bond, debenture or other paper or document;

            (g) the Pass Through Trustee may execute any of the trusts or powers
hereunder or perform any duties hereunder either directly or by or through
agents or attorneys and the Pass Through Trustee shall not be responsible for
any misconduct or negligence on the part of any agent or attorney appointed by
it hereunder with due care;

            (h) the Pass Through Trustee shall not be personally liable for any
action taken, suffered or omitted by it in good faith and believed by it to be
authorized or within the discretion of rights or powers conferred upon it by
this Pass Through Trust Agreement;

            (i) the right of the Pass Through Trustee to perform any
discretionary act enumerated in this Pass Through Trust Agreement shall not be
construed as a duty, and the Pass Through Trustee shall not be answerable for
other than its negligence or willful misconduct in the performance of such act;

            (j) the Pass Through Trustee shall not be required to give any bond
or surety in respect of the execution of the trust fund created hereby or the
powers granted hereunder; and

            (k) the Pass Through Trustee shall have no responsibility for filing
any financing or continuation statement in any public office at any time or to
otherwise perfect or maintain the perfection of any security interest or lien
granted to it hereunder or to record this Pass Through Trust Agreement.


                                       30
<PAGE>   36
      Section 7.4. Not Responsible for Recitals; Issuance of Certificates. The
recitals contained herein and in the Certificates, except the certificates of
authentication, shall not be taken as the statements of the Pass Through
Trustee, and the Pass Through Trustee assumes no responsibility for their
correctness. The Pass Through Trustee makes no representations as to the
validity or sufficiency of this Pass Through Trust Agreement, the Lessor Notes,
the Lessor Note Documents, or the Certificates, or the collateral securing the
Lessor Notes, except that the Pass Through Trustee hereby represents and
warrants that this Pass Through Trust Agreement has been, and each Certificate
will be, executed and delivered by one of its officers who is duly authorized to
execute and deliver such document on its behalf.

      Section 7.5. May Hold Certificates. The Pass Through Trustee, any Paying
Agent, Registrar or any other agent, in their respective individual or any other
capacity, may become the owner or pledgee of Certificates and may otherwise deal
with the Company, Owner Lessor, Owner Participant or Lease Indenture Trustee
with the same rights it would have if it were not the Pass Through Trustee,
Paying Agent, Registrar or such other agent, subject to Section 7.8 in the case
of the Pass Through Trustee.

      Section 7.6. Money Held in Pass Through Trust. Money held by the Pass
Through Trustee or the Paying Agent in trust hereunder need not be segregated
from other funds except to the extent required herein or by law and neither the
Pass Through Trustee nor the Paying Agent shall have any liability for interest
upon any such moneys except as provided for herein.

      Section 7.7. Compensation, Reimbursement and Indemnification. The Company
agrees:

            (1) to pay, or cause to be paid, to the Pass Through Trustee from
      time to time the compensation separately agreed to by the Pass Through
      Trustee and PPL Montana for all services rendered by it hereunder (which
      compensation shall not be limited by any provision of law in regard to the
      compensation of a trustee of an express trust); and

            (2) except as otherwise expressly provided herein, to reimburse, or
      cause to be reimbursed, the Pass Through Trustee upon its request for all
      reasonable out-of-pocket expenses, disbursements and advances incurred or
      made by the Pass Through Trustee in accordance with any provision of this
      Pass Through Trust Agreement (including the reasonable compensation and
      the expenses and disbursements of its agents and counsel), except any such
      expense, disbursement or advance as may be attributable to its negligence,
      willful misconduct or bad faith.

            In addition, the Pass Through Trustee shall be entitled to
reimbursement from, and shall have a lien prior to the Certificates upon, all
property and funds held or collected by the Pass Through Trustee in its capacity
as Pass Through Trustee for any tax incurred without negligence, bad faith or
willful misconduct, on its part, arising out of or in connection with the
acceptance or administration of this Pass Through Trust (other than any tax
attributable to the Pass Through Trustee's compensation for serving as such),
including any costs and expenses incurred in contesting the imposition of any
such tax. If the Pass Through Trustee reimburses itself for any such tax, it
will within 30 days mail a brief report setting forth the circumstances thereof
to all Certificateholders as their names and addresses appear in the Register.


                                       31
<PAGE>   37
      Section 7.8. Corporate Trustee Required; Eligibility. There shall at all
times be a Pass Through Trustee hereunder which (a) shall be, at any time that
the Certificates shall be subject to the Trust Indenture Act, a Person eligible
to act as a trustee under Section 310(a) of the Trust Indenture Act and (b)
shall be a corporation organized and doing business under the laws of the United
States of America or of any state, authorized under such laws to exercise
corporate trust powers, having a combined capital and surplus of at least
$150,000,000, and subject to supervision or examination by Federal or state
authority. If such corporation publishes reports of condition at least annually,
pursuant to law or to the requirements of the aforesaid supervising or examining
authority, then for the purposes of this Section 7.8, the combined capital and
surplus of such corporation shall be deemed to be its combined capital and
surplus as set forth in its most recent report of condition so published. If at
any time the Pass Through Trustee shall cease to be eligible in accordance with
the provisions of clause (a) of this Section 7.8 at a time when it is required
to be so qualified, it shall resign immediately in the manner and with the
effect hereinafter specified in this Section 7.

      Section 7.9. Resignation and Removal: Appointment of Successor.

            (a) No resignation or removal of the Pass Through Trustee and no
appointment of a successor Pass Through Trustee pursuant to this Section 7.9
shall become effective until the acceptance of appointment by the successor Pass
Through Trustee under Section 7.10.

            (b) The Pass Through Trustee may resign at any time by giving
written notice thereof to the Company, the Authorized Agents, each Owner Lessor,
each Owner Participant and each Lease Indenture Trustee. If an instrument of
acceptance by a successor Pass Through Trustee shall not have been delivered to
the Company, each Owner Lessor, each Owner Participant and each Lease Indenture
Trustee within 30 days after the giving of such notice of resignation, the
resigning Pass Through Trustee may petition any court of competent jurisdiction
for the appointment of a successor Pass Through Trustee.

            (c) The Pass Through Trustee may be removed at any time by Act of
the Holders holding Certificates evidencing Fractional Undivided Interests
aggregating not less than a majority in interest in the Pass Through Trust
delivered to the Pass Through Trustee and to the Company, each Owner Lessor and
each Lease Indenture Trustee.

            (d) If at any time:

                  (1) the Pass Through Trustee fails to, at any time that the
            Certificates shall be subject to the Trust Indenture Act, comply
            with the requirements of Section 310 of the Trust Indenture Act
            after written request for such compliance by a Certificateholder
            that has been a bona fide Certificateholder for at least six months;
            or

                  (2) the Pass Through Trustee shall cease to be eligible under
            Section 7.8 hereof and shall fail to resign after written request
            therefor by the Company (or, following the occurrence of a Lease
            Event of Default, the applicable Owner Lessor) or by any such
            Certificateholder; or


                                       32
<PAGE>   38
                  (3) the Pass Through Trustee shall become incapable of acting
            or shall be adjudged bankrupt or insolvent or a receiver of the Pass
            Through Trustee or of its property shall be appointed or any public
            officer shall take charge or control of the Pass Through Trustee or
            of its property or affairs for the purpose of rehabilitation,
            conservation or liquidation;

then, in any case, (i) the Company (or, following the occurrence of a Lease
Event of Default, the applicable Owner Lessor), may remove the Pass Through
Trustee or (ii) subject to Section 6.6 hereof, any Certificateholder who has
been a bona fide Holder of a Certificate for at least six months may, on behalf
of himself and all others similarly situated, petition any court of competent
jurisdiction for the removal of the Pass Through Trustee and the appointment of
a successor Pass Through Trustee.

            (e) If a Responsible Officer of the Pass Through Trustee shall
obtain Actual Knowledge of an Avoidable Tax (as hereinafter defined) which has
been or is likely to be asserted, the Pass Through Trustee shall promptly notify
the Company and the Owner Lessors thereof and shall, within 30 days of such
notification, resign hereunder unless within such 30-day period the Pass Through
Trustee shall have received notice that the Company or the Owner Lessors have
agreed to pay such tax. The Company shall promptly appoint a successor Pass
Through Trustee in a jurisdiction where there are no Avoidable Taxes. As used
herein an "Avoidable Tax" means a state or local tax: (i) upon (w) the Pass
Through Trust, (x) the Trust Property, (y) Holders of the Certificates or (z)
the Pass Through Trustee for which the Pass Through Trustee is entitled to seek
reimbursement from the Trust Property, and (ii) that would be avoided if the
Pass Through Trustee were located in another state, or jurisdiction within a
state, within the United States. A tax shall not be an Avoidable Tax if the
Company or the Owner Lessors shall agree to pay, and shall pay, such tax.

            (f) If the Pass Through Trustee shall resign, be removed or become
incapable of acting, or if a vacancy shall occur in the office of the Pass
Through Trustee for any cause, the Company (or, following the occurrence of a
Lease Event of Default, the applicable Owner Lessor) shall promptly appoint a
successor Pass Through Trustee. If, within one year after such resignation,
removal or incapability, or the occurrence of such vacancy, a successor Pass
Through Trustee shall be appointed by Act of the Holders holding Certificates
evidencing Fractional Undivided Interests aggregating not less than a majority
in interest in the Pass Through Trust, delivered to the Company, the Owner
Lessors, the Owner Participants, the Lease Indenture Trustees and the retiring
Pass Through Trustee, the successor Pass Through Trustee so appointed shall,
forthwith upon its acceptance of such appointment, become the successor Pass
Through Trustee and supersede the successor Pass Through Trustee appointed as
provided above. If no successor Pass Through Trustee shall have been so
appointed as provided above and accepted appointment in the manner hereinafter
provided, any Certificateholder who has been a bona fide Holder of a Certificate
for at least six months may, on behalf of himself and all others similarly
situated, petition any court of competent jurisdiction for the appointment of a
successor Pass Through Trustee.

            (g) The successor Pass Through Trustee shall give notice of the
resignation and removal of the Pass Through Trustee and appointment of the
successor Pass Through Trustee by mailing written notice of such event by
first-class mail, postage prepaid, to the


                                       33
<PAGE>   39
Holders of Certificates as their names and addresses appear in the Register.
Each notice shall include the name of such successor trustee and the address of
its Corporate Trust Office.

      Section 7.10. Acceptance of Appointment by Successor. Every successor Pass
Through Trustee appointed hereunder shall execute, acknowledge and deliver to
the Company, the Owner Lessors and to the retiring Pass Through Trustee an
instrument accepting such appointment, and thereupon the resignation or removal
of the retiring Pass Through Trustee shall become effective and such successor
Pass Through Trustee, without any further act, deed or conveyance, shall become
vested with all the rights, powers, trusts and duties of the retiring Pass
Through Trustee; but, on request of the Company (or, following the occurrence of
a Lease Event of Default, the applicable Owner Lessor) to the successor Pass
Through Trustee, such retiring Pass Through Trustee shall execute and deliver an
instrument transferring to such successor Pass Through Trustee all the rights,
powers and trusts of the retiring Pass Through Trustee and shall duly assign,
transfer and deliver to such successor Pass Through Trustee all property and
money held by such retiring Pass Through Trustee hereunder, subject nevertheless
to its lien, if any, provided for in Section 7.7. Upon request of any such
successor Pass Through Trustee, the Company, the Owner Lessors, the retiring
Pass Through Trustee and such successor Pass Through Trustee shall execute and
deliver any and all instruments containing such provisions as shall be necessary
or desirable to transfer and confirm to, and for more fully and certainly
vesting in, such successor Pass Through Trustee all such rights, powers and
trusts.

            No successor Pass Through Trustee shall accept its appointment
unless at the time of such acceptance such successor Pass Through Trustee shall
be qualified and eligible under this Section 7.

      Section 7.11. Merger, Conversion, Consolidation or Succession to Business.
Any Person into which the Pass Through Trustee may be merged or converted or
with which it may be consolidated, or any Person resulting from any merger,
conversion or consolidation to which the Pass Through Trustee shall be a party,
or any Person succeeding to all or substantially all of the corporate trust
business of the Pass Through Trustee, shall be the successor of the Pass Through
Trustee hereunder, provided such Person shall be otherwise qualified and
eligible under this Section 7, without the execution or filing of any paper or
any further act on the part of any of the parties hereto. In case any
Certificates shall have been authenticated, but not delivered, by the Pass
Through Trustee then in office, any successor by merger, conversion or
consolidation to such authenticating Pass Through Trustee may adopt such
authentication and deliver the Certificates so authenticated with the same
effect as if such successor Pass Through Trustee had itself authenticated such
Certificates.

      Section 7.12. Maintenance of Agencies.

            (a) There shall at all times be maintained in the Borough of
Manhattan, The City of New York, an office or agency where Certificates may be
presented or surrendered for registration of transfer or for exchange, and for
payment thereof and where notices and demands to or upon the Pass Through
Trustee in respect of the Certificates or of this Pass Through Trust Agreement
may be served. Written notice of the location of each such other office or
agency and of any change of location thereof shall be given by the Pass Through
Trustee to the Company, each Owner Lessor, each Owner Participant, each Lease
Indenture Trustee and the


                                       34
<PAGE>   40
Certificateholders. In the event that no such office or agency shall be
maintained or no such notice of location or of change of location shall be
given, presentations and demands may be made and notices may be served at the
Corporate Trust Office of the Pass Through Trustee.

            (b) There shall at all times be a Registrar and a Paying Agent
hereunder. Each such Authorized Agent shall be a bank or trust company, shall be
a corporation organized and doing business under the laws of the United States
or any state, with a combined capital and surplus of at least $150,000,000, and
shall be authorized under such laws to exercise corporate trust powers, subject
to supervision by Federal or state authorities. The Pass Through Trustee shall
initially be the Paying Agent and, as provided in Section 3.4, Registrar
hereunder. Each Registrar shall furnish to the Pass Through Trustee (unless they
are the same entity), at stated intervals of not more than six months, and at
such other times as the Pass Through Trustee may request in writing, a copy of
the Register.

            (c) Any Person into which any Authorized Agent may be merged or
converted or with which it may be consolidated, or any Person resulting from any
merger, consolidation or conversion to which any Authorized Agent shall be a
party, or any Person succeeding to the corporate trust business of any
Authorized Agent, shall be the successor of such Authorized Agent hereunder, if
such successor Person is otherwise eligible under this Section 7.12, without the
execution or filing of any paper or any further act on the part of the parties
hereto or such Authorized Agent or such successor Person.

            (d) Any Authorized Agent may at any time resign by giving written
notice of resignation to the Pass Through Trustee, the Company, each Owner
Lessor, each Owner Participant and each Lease Indenture Trustee. The Company
(or, following the occurrence of a Lease Event of Default, the applicable Owner
Lessor) may, and at the request of the Pass Through Trustee shall, at any time
terminate the agency of any Authorized Agent by giving written notice of
termination to such Authorized Agent and to the Pass Through Trustee. Upon the
resignation or termination of an Authorized Agent or in case at any time any
such Authorized Agent shall cease to be eligible under this Section 7.12 (when,
in either case, no other Authorized Agent performing the functions of such
Authorized Agent shall have been appointed), the Company (or, following the
occurrence of a Lease Event of Default, the applicable Owner Lessor) shall
promptly appoint one or more qualified successor Authorized Agents reasonably
satisfactory to the Pass Through Trustee, to perform the functions of the
Authorized Agent which has resigned or whose agency has been terminated or who
shall have ceased to be eligible under this Section 7.12. The Company (or,
following the occurrence of a Lease Event of Default, the applicable Owner
Lessor) shall give written notice of any such appointment made by it to the Pass
Through Trustee, the Company, each Owner Lessor and each Lease Indenture
Trustee; and in each case the Pass Through Trustee shall mail notice of such
appointment to all Holders as their names and addresses appear on the Register.

            (e) The Company agrees to pay, or cause to be paid, from time to
time to each Authorized Agent the compensation as set forth in the schedule
agreed to by each Authorized Agent and PPL Montana for its services and to
reimburse it for its reasonable expenses.

      Section 7.13. Money for Certificate Payments to Be Held in Trust. All
moneys deposited with any Paying Agent for the purpose of any payment on
Certificates shall be


                                       35
<PAGE>   41
deposited in a non interest bearing account and held in trust for the benefit of
the Holders of the Certificates entitled to such payment, subject to the
provisions of this Section 7.13. Moneys so deposited and held in trust shall
constitute a separate trust fund for the benefit of the Holders of the
Certificates with respect to which such money was deposited.

            The Pass Through Trustee will cause each Paying Agent other than the
Pass Through Trustee to execute and deliver to it an instrument in which such
Paying Agent shall agree with the Pass Through Trustee, subject to the
provisions of this Section 7.13, that such Paying Agent will:

            (1) hold all sums held by it for payments on Certificates in trust
      for the benefit of the Persons entitled thereto until such sums shall be
      paid to such Persons or otherwise disposed of as herein provided;

            (2) give the Pass Through Trustee notice in writing of any default
      by any obligor upon the Lessor Notes in the making of any such payment;
      and

            (3) at any time during the continuance of any such default, upon the
      written request of the Pass Through Trustee, forthwith pay to the Pass
      Through Trustee all sums so held in trust by such Paying Agent.

            The Pass Through Trustee may at any time, for the purpose of
obtaining the satisfaction and discharge of this Pass Through Trust Agreement or
for any other purpose, direct any Paying Agent to pay to the Pass Through
Trustee all sums held in trust by such Paying Agent, such sums to be held by the
Pass Through Trustee upon the same trusts as those upon which such sums were
held by such Paying Agent; and, upon such payment by any Paying Agent to the
Pass Through Trustee, such Paying Agent shall be released from all further
liability with respect to such money.

      Section 7.14. Registration of Lessor Notes in Pass Through Trustee's Name.
The Pass Through Trustee agrees that all Lessor Notes and Permitted Government
Investments, if any, shall be issued in the name of the Pass Through Trustee or
its nominee and held by the Pass Through Trustee, or, if not so held, the Pass
Through Trustee or its nominee shall be reflected as the owner of such Lessor
Notes or Permitted Government Investments, as the case may be, in the register
of the issuer of such Lessor Notes or Permitted Government Investments under the
applicable provisions of the Uniform Commercial Code in effect where the Pass
Through Trustee holds such Lessor Notes or Permitted Government Investments, or
other applicable law then in effect.

      Section 7.15. Withholding Taxes; Information Reporting. The Pass Through
Trustee, as trustee, shall exclude and withhold from each distribution of
principal, premium, if any, and interest and other amounts due hereunder or
under the Certificates any and all withholding taxes applicable thereto as
required by law. The Pass Through Trustee agrees (i) to act as such withholding
agent and, in connection therewith, whenever any present or future taxes or
similar charges are required to be withheld with respect to any amounts payable
in respect of the Certificates, to withhold such amounts and timely pay the same
to the appropriate authority in the name of and on behalf of the Holders of the
Certificates, (ii) that it will file any necessary


                                       36
<PAGE>   42
withholding tax returns or statements when due, and (iii) that, as promptly as
possible after the payment thereof, it will deliver to each Holder of a
Certificate appropriate documentation showing the payment thereof, together with
such additional documentary evidence as such Holders may reasonably request from
time to time. The Pass Through Trustee agrees to file any other information
reports as it may be required to file under United States law. Any amounts
withheld and paid to a relevant taxing authority pursuant to this Section 7.15
shall be deemed to have been paid to the related Certificateholders for all
purposes under the Operative Documents.

SECTION 8. CERTIFICATEHOLDERS' LISTS AND REPORTS

      Section 8.1. The Company to Furnish Pass Through Trustee with Names and
Addresses of Certificateholder. The Company will furnish to the Pass Through
Trustee within fifteen days after each Record Date with respect to a Scheduled
Payment, and at such other times as the Pass Through Trustee may request in
writing, a list, in such form as the Pass Through Trustee may reasonably
require, of all information in the possession or control of the Company as to
the names and addresses of the Holders of Certificates, in each case as of a
date not more than fifteen days prior to the time such list is furnished;
provided, however, that so long as the Pass Through Trustee is the sole
Registrar, no such list need be furnished; and provided, further, however, that
no such list need be furnished for so long as a copy of the Register is being
furnished to the Pass Through Trustee pursuant to Section 7.12(b).

      Section 8.2. Preservation of Information. The Pass Through Trustee shall
preserve, in as current a form as is reasonably practicable, the names and
addresses of Holders of Certificates contained in the most recent list furnished
to the Pass Through Trustee as provided in Section 7.12(b) or Section 8.1, as
the case may be, and the names and addresses of Holders of Certificates received
by the Pass Through Trustee in its capacity as Registrar, if so acting. The Pass
Through Trustee may destroy any list furnished to it as provided in Section
7.12(b) or Section 8.1, as the case may be, upon receipt of a new list so
furnished.

      Section 8.3. Reports by the Company. The Company shall, at any time that
the Certificates shall be subject to the Trust Indenture Act, comply with
Section 314 of the Trust Indenture Act and shall file, furnish and deliver the
reports, information, documents, certificates and opinions required thereunder,
and, at any time that the Certificates shall be subject to the Trust Indenture
Act, acknowledge and agree that, for purposes of Section 314 of the Trust
Indenture Act, the Company shall be considered to be the "obligor" upon the
Certificates. Without limiting the generality of the foregoing, at any time that
the Certificates shall be subject to the Trust Indenture Act, the Company shall
deliver to the Pass Through Trustee the annual certificate required under clause
(4) of Section 314(a) of the Trust Indenture Act within 120 days following the
end of each fiscal year of the Company (which ends on December 31) ending after
the date hereof. The provisions of this Section 8.3 shall not be construed to
impose any obligation or liability on the Company to pay any of the principal,
premium, if any, or interest in respect of the Lessor Notes or the Certificates.

      Section 8.4. Reports by the Pass Through Trustee. On or before each May
15, the Pass Through Trustee shall, at any time that the Certificates shall be
subject to the Trust Indenture Act, transmit, in the manner and to the extent
required by Section 313(c) of the Trust Indenture Act, any report dated as of
such May 15, in accordance with and to the extent required under


                                       37
<PAGE>   43
Section 313 of the Trust Indenture Act. Additionally, the Pass Through Trustee
shall comply with the reporting requirements imposed under Treasury Regulation
1.67.

SECTION 9. SUPPLEMENTAL TRUST AGREEMENTS

      Section 9.1. Supplemental Trust Agreement Without Consent of
Certificateholders. Without the consent of the Holder of any Certificates, the
Company may, and the Pass Through Trustee (subject to Section 9.3) shall, at any
time and from time to time enter into one or more agreements supplemental
hereto, in form satisfactory to the Pass Through Trustee, for any of the
following purposes:

            (1) to evidence the succession of another corporation to the Company
      and the assumption by any such successor of the obligations of the Company
      herein contained;

            (2) to add to the covenants of the Company, for the protection of
      the Holders of the Certificates;

            (3) to surrender any right or power herein conferred upon the
      Company;

            (4) to cure any ambiguity, to correct or supplement any provision
      herein which may be defective or inconsistent with any other provision
      herein or to make any other provisions with respect to matters or
      questions arising under this Pass Through Trust Agreement; provided that
      any such action will not adversely affect the interests of the Holders of
      the Certificates;

            (5) to correct or amplify the description of property that
      constitutes Trust Property or the conveyance of such property to the Pass
      Through Trustee;

            (6) to evidence and provide for a successor Pass Through Trustee;

            (7) to comply with requirements of the Commission, any applicable
      law, rules or regulations of any exchange or quotation system on which the
      Certificates are listed, or any regulatory body;

            (8) at any time that the Certificates shall be subject to the Trust
      Indenture Act, to modify, eliminate or add to the provisions of this Pass
      Through Trust Agreement to the extent as shall be necessary to qualify or
      continue the qualification of this Pass Through Trust Agreement (including
      any supplemental agreement) under the Trust Indenture Act or under any
      similar Federal statute hereafter enacted, or to add to this Pass Through
      Trust Agreement such other provisions as may be expressly permitted by the
      Trust Indenture Act, excluding, however, the provisions referred to in
      Section 316(a)(2) of the Trust Indenture Act as in effect at the date as
      of which this instrument was executed or any corresponding provision in
      any similar Federal statute hereafter enacted;

            (9) to modify, amend or supplement any provision herein to reflect
      changes relating to the assumption and substitution of any Lessor Note
      pursuant to Section 2.10(b) of the applicable Lease Indenture;


                                       38
<PAGE>   44
            (10) to add, eliminate, or change any provision under this Pass
      Through Trust Agreement that will not adversely affect the interests of
      the Certificateholders; or

            (11) if necessary in the opinion of the Company, to provide for
      issuance of Exchange Certificates as contemplated by the Registration
      Rights Agreements;

provided that in each case the Pass Through Trustee shall have received an
opinion of counsel, which may be counsel to the Company, to the effect that such
supplemental agreement does not cause the Pass Through Trust to become taxable
as an "association" within the meaning of Treasury Regulation Section 301.7701-4
or to be taxable as other than a pass through entity for Federal income tax
purposes.

      Section 9.2. Supplemental Trust Agreements with Consent of
Certificateholders. With the consent of the Holders of Certificates evidencing
Fractional Undivided Interests aggregating not less than a majority in interest
of the Fractional Undivided Interests evidenced by all Certificates at the time
Outstanding (determined as provided in Section 1.4(c) hereof), by Act of said
Holders delivered to the Company and the Pass Through Trustee, the Company may
(with the consent of the Owner Lessor, such consent not to be unreasonably
withheld), and the Pass Through Trustee (subject to Section 9.3 hereof) shall,
enter into an agreement or agreements supplemental hereto for the purpose of
adding any provisions to or changing in any manner or eliminating any of the
provisions of this Pass Through Trust Agreement or of modifying in any manner
the rights and obligations of the Holders of the Certificates under this Pass
Through Trust Agreement; provided, however, that no such supplemental agreement
shall, without the consent of the Holder of each Outstanding Certificate
affected thereby:

            (1) reduce in any manner the amount of, or delay the timing of, any
      receipt by the Pass Through Trustee of payments on the Lessor Notes held
      in the Pass Through Trust, or distributions that are required to be made
      herein on any Certificate of such Pass Through Trust, or change any date
      of payment on any such Certificate, or change the place of payment where,
      or the coin or currency in which, any such Certificate is payable, or
      impair the right of any Holder of any such Certificate to institute suit
      for the enforcement of any such payment or distribution on or after the
      Distribution Date or Special Distribution Date applicable thereto; or

            (2) except as provided in this Pass Through Trust Agreement, permit
      the disposition of any Lessor Note in the Trust Property, or permit the
      creation of any lien on the Trust Property, or otherwise deprive any
      Certificateholder of the benefit of the ownership of the Lessor Notes held
      in the Pass Through Trust or the lien of the related Lease Indenture; or

            (3) reduce the percentage of the aggregate Fractional Undivided
      Interests which is required to approve any such supplemental agreement, or
      reduce such percentage required for any waiver provided for in this Pass
      Through Trust Agreement.

Notwithstanding the foregoing, no such supplemental agreement shall be entered
into unless the Pass Through Trustee shall have received an opinion of counsel,
which may be counsel to the Company, to the effect that such supplemental
agreement does not cause the Pass Through Trust


                                       39
<PAGE>   45
to become taxable as an "association", within the meaning of Treasury Regulation
Section 301.7701-4 or to be taxable as other than a pass through entity for
Federal income tax purposes.

            It shall not be necessary for any Act of Certificateholders under
this Section 9.2 to approve the particular form of any proposed supplemental
agreement, but it shall be sufficient if such Act shall approve the substance
thereof.

      Section 9.3. Documents Affecting Immunity or Indemnity. If in the opinion
of the Pass Through Trustee any document required to be executed by it pursuant
to the terms of Section 9.1 or 9.2 affects any interest, right, duty, immunity
or indemnity in favor of the Pass Through Trustee under this Pass Through Trust
Agreement, the Pass Through Trustee may in its discretion decline to execute
such document.

      Section 9.4. Execution of Supplemental Trust Agreements. In executing, or
accepting the additional trusts created by, any supplemental agreement permitted
by this Section 9 or the modification thereby of the trusts created by this Pass
Through Trust Agreement, the Pass Through Trustee shall be entitled to receive,
and (subject to Section 7.1) shall be fully protected in relying upon, an
Opinion of Counsel stating that the execution of such supplemental agreement is
authorized or permitted by this Pass Through Trust Agreement.

      Section 9.5. Effect of Supplemental Trust Agreements. Upon the execution
of any supplemental agreement under this Section 9, this Pass Through Trust
Agreement shall be modified in accordance therewith, and such supplemental
agreement shall form a part of this Pass Through Trust Agreement for all
purposes; and every Holder of Certificates theretofore or thereafter
authenticated and delivered hereunder shall be bound thereby.

      Section 9.6. Reference in Certificates to Supplemental Trust Agreements.
Certificates authenticated and delivered after the execution of any supplemental
agreement pursuant to this Section 9 may bear a notation in form approved by the
Pass Through Trustee as to any matter provided for in such supplemental
agreement; and, in such case, suitable notation may be made upon Outstanding
Certificates after proper presentation and demand.

      Section 9.7. Conformity with Trust Indenture Act. Every supplemental
agreement under this Section 9 executed at a time that the Certificates shall be
subject to the Trust Indenture Act, shall conform to requirements of the Trust
Indenture Act as in effect on the date such supplemental agreement is executed.

SECTION 10. AMENDMENTS AND CONSENTS TO LEASE INDENTURES AND OTHER LESSOR NOTE
            DOCUMENTS

            (a) In the event that the Pass Through Trustee, as holder of any
Lessor Note in trust for the benefit of the Certificateholders, receives a
request for a consent to any amendment, modification, waiver or supplement under
any Lease Indenture or other Lessor Note Document that requires the consent of
the holder of such Lessor Note, the Pass Through Trustee shall forthwith send a
notice of such proposed amendment, modification, waiver or supplement to each
Certificateholder registered on the Register as of such date. Any such notice
shall describe the proposed amendment, modification, waiver or supplement (or
attach a copy thereof). The Pass Through Trustee shall request from the
Certificateholders Directions as to (i) whether or not


                                       40
<PAGE>   46
to direct the applicable Lease Indenture Trustee to take or refrain from taking
any action which a holder of such Lessor Note has the option to direct, (ii)
whether or not to give or execute any waivers, consents, amendments,
modifications or supplements as a holder of such Lessor Note and (iii) how to
vote any Lessor Note if a vote has been called for with respect thereto. Any
such request shall specify a date by which Certificateholders are requested to
respond. Provided such a request for Certificateholder Direction shall have been
made, in directing any action or casting any vote or giving any consent as the
holder of any Lessor Note, the Pass Through Trustee shall vote or consent with
respect to such Lessor Note in the same proportion as the Certificates were
actually voted by Acts of Holders delivered to the Pass Through Trustee prior to
two Business Days before the Pass Through Trustee directs such action or casts
such vote or gives such consent. Notwithstanding the foregoing, but subject to
Section 6.4, in the case that an Event of Default hereunder shall have occurred
and be continuing, the Pass Through Trustee may, in its own discretion and at
its own direction, consent and notify the applicable Lease Indenture Trustee of
such consent to any amendment, modification, waiver or supplement under a Lease
Indenture or other Lessor Note Document.

            (b) With respect to consents, approvals, waivers and authorizations
which under the terms of Section 8 of the Lease Indenture may be given by the
Lease Indenture Trustee without the necessity of the consent of any of the
holders of Lessor Notes, no consent, approval, waiver or authorization shall be
required hereunder on the part of the Pass Through Trustee or the
Certificateholders.

            (c) PPL Montana will not consent to an optional refinancing of any
Lessor Note by the Owner Lessor pursuant to Section 10.2(d)(ii) of the
applicable Lease Indenture unless each of the other Owner Lessors shall
simultaneously prepay its Lessor Note.

SECTION 11. TERMINATION OF PASS THROUGH TRUST

      Section 11.1. Termination of the Pass Through Trust. The respective
obligations and responsibilities of the Company and the Pass Through Trustee
created hereby and the Pass Through Trust created hereby shall terminate upon
the distribution to all Certificateholders of all amounts required to be
distributed to them pursuant to this Pass Through Trust Agreement and the
disposition of all property held as part of the Trust Property; provided,
however, that if and to the extent that any of the options, rights and
privileges granted under this Pass Through Trust Agreement, would, in the
absence of the limitation imposed by this sentence, be invalid or unenforceable
as being in violation of the rule against perpetuities or any other rule or law
relating to the vesting of interest in property or the suspension of the power
of alienation of property, then it is agreed that notwithstanding any other
provision of this Pass Through Trust Agreement, such options, rights and
privileges, subject to the respective conditions hereof governing the exercise
of such options, rights and privileges, will be exercisable only during (a) the
longer of (i) a period which will end twenty-one (21) years after the death of
the last survivor of the descendants living on the date of the execution of this
Pass Through Trust Agreement of the following Presidents of the United States:
Franklin D. Roosevelt, Harry S. Truman, Dwight D. Eisenhower, John F. Kennedy,
Lyndon B. Johnson, Richard M. Nixon, Gerald R. Ford, James E. Carter, Ronald W.
Reagan, George H.W. Bush and William J. Clinton or (ii) the period provided
under the Uniform Statutory Rule Against Perpetuities or (b) the


                                       41
<PAGE>   47
specific applicable period of time expressed in this Pass Through Trust
Agreement, whichever of (a) or (b) is shorter.

            Notice of any termination, specifying the Distribution Date (or
Special Distribution Date, as the case may be) upon which the Certificateholders
may surrender their Certificates to the Pass Through Trustee for payment of the
final distribution and cancellation, shall be mailed promptly by the Pass
Through Trustee to Certificateholders not earlier than the 60th day and not
later than the 20th day next preceding such final distribution specifying (A)
the Distribution Date (or Special Distribution Date, as the case may be) upon
which final payment of the Certificates will be made upon presentation and
surrender of Certificates at the office or agency of the Pass Through Trustee
therein specified, (B) the amount of any such final payment, and (C) that the
Record Date otherwise applicable to such Distribution Date (or Special
Distribution Date, as the case may be) is not applicable, payments being made
only upon presentation and surrender of the Certificates at the office or agency
of the Pass Through Trustee therein specified. The Pass Through Trustee shall
give such notice to the Registrar at the time such notice is given to
Certificateholders. Upon presentation and surrender of the Certificates, the
Pass Through Trustee shall cause to be distributed to Certificateholders amounts
distributable on such Distribution Date or Special Distribution Date, as the
case may be, pursuant to Section 4.2 hereof.

            In the event that all of the Certificateholders shall not surrender
their Certificates for cancellation within six months after the date specified
in the above mentioned written notice, the Pass Through Trustee shall give a
second written notice to the remaining Certificateholders to surrender their
Certificates for cancellation and receive the final distribution with respect
thereto. In the event that any money held by the Pass Through Trustee for the
payment of distributions on the Certificates shall remain unclaimed for two
years (or such lesser time as the Pass Through Trustee shall be satisfied, after
sixty days' written notice from the Company, is one month prior to the escheat
period provided under applicable law) after the final distribution date with
respect thereto, the Pass Through Trustee shall pay to each Lease Indenture
Trustee the appropriate amount of money relating to such Lease Indenture Trustee
and shall give written notice thereof to each Owner Lessor, each Owner
Participant and the Company.

SECTION 12. MISCELLANEOUS PROVISIONS

      Section 12.1. Amendments and Waivers. No term, covenant, agreement or
condition of this Pass Through Trust Agreement may be terminated, amended or
compliance therewith waived (either generally or in a particular instance,
retroactively or prospectively) except by an instrument or instruments in
writing executed by each party hereto.

      Section 12.2. Limitation on Rights of Certificateholders. The death or
incapacity of any Certificateholder shall not operate to terminate this Pass
Through Trust Agreement or the Pass Through Trust, nor entitle such
Certificateholder's legal representatives or heirs to claim an accounting or to
take any action or commence any proceeding in any court for a partition or
winding up of the Pass Through Trust, nor otherwise affect the rights,
obligations and liabilities of the parties hereto or any of them.


                                       42
<PAGE>   48
      Section 12.3. Certificates Nonassessable and Fully Paid.
Certificateholders shall not be personally liable for obligations of the Pass
Through Trust, the Fractional Undivided Interests represented by the
Certificates shall be nonassessable for any losses or expenses of the Pass
Through Trust or for any reason whatsoever, and Certificates upon authentication
thereof by the Pass Through Trustee pursuant to Section 3.2 hereof are and shall
be deemed fully paid. No Certificateholder shall have any right (except as
expressly provided herein) to vote or in any manner otherwise control the
operation and management of the Trust Property, the Pass Through Trust
established hereunder, or the obligations of the parties hereto, nor shall
anything set forth herein, or contained in the terms of the Certificates, be
construed so as to constitute the Certificateholders from time to time as
partners or members of an association.

      Section 12.4. Notices. Unless otherwise expressly specified or permitted
by the terms hereof, all communications and notices provided for herein to a
party hereto shall be in writing or by a telecommunications device capable of
creating a written record, and any such notice shall become effective (a) upon
personal delivery thereof, including by overnight mail or courier service, (b)
in the case of notice by United States mail, certified or registered, postage
prepaid, return receipt requested, upon receipt thereof, or (c) in the case of
notice by such a telecommunications device, upon transmission thereof, provided
such transmission is promptly confirmed by either of the methods set forth in
clauses (a) or (b) above, in each case addressed to such party and copy party at
its address set forth below or at such other address as such party or copy party
may from time to time designate by written notice to the other party:

            If to PPL Montana, LLC:

                  303 North Broadway, Suite 400
                  Billings, MT  59101
                  Telephone No.: (406) 869-5100
                  Facsimile No.: (406) 869-5149
                  Attention:  Vice President and General Counsel

            If to the Pass Through Trustee:

                  The Chase Manhattan Bank
                  Capital Markets Fiduciary Services
                  450 West 33rd Street, 15th Floor
                  New York, New York 10001-2697
                  Telephone No.:    (212) 946-7557
                  Facsimile No.: (212) 946-8177/8
                  Attention:  Annette M. Marsula


      Section 12.5. Successors and Assigns.

            (a) This Pass Through Trust Agreement shall be binding upon and
shall inure to the benefit of, and shall be enforceable by, the parties hereto
and their respective successors and assigns as permitted by and in accordance
with the terms hereof.


                                       43
<PAGE>   49
            (b) Except as expressly provided herein or in the other Operative
Documents, no party hereto may assign its interests or transfer its obligations
herein without the consent of the other parties hereto.

      Section 12.6. Business Day. In any case where any Distribution Date or
Special Distribution Date relating to any Certificate is not a Business Day,
then (notwithstanding any other provision of this Pass Through Trust Agreement)
the payment otherwise payable on such date shall be payable on the next
succeeding Business Day with the same force and effect as if made on such
Distribution Date or Special Distribution Date and (provided that such payment
is made on such succeeding Business Day) no interest shall accrue on the amount
of such payment from and after such scheduled date to the time of such payment
on such next succeeding Business Day.

      Section 12.7. Governing Law. This Pass Through Trust Agreement, the
Certificates and the rights and duties of the parties hereunder and thereunder
shall be in all respects governed by and construed in accordance with the law of
the State of New York, including all matters of construction, validity and
performance (without giving effect to the conflicts of laws provisions thereof,
other than New York General Obligations Law Section 5-1401).

      Section 12.8. Severability. Any provision of this Pass Through Trust
Agreement that is prohibited or unenforceable in any jurisdiction shall, as to
such jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions hereof, and any
such prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction.

      Section 12.9. Benefits of Pass Through Trust Agreement. Nothing in this
Pass Through Trust Agreement or in the Certificates, express or implied, shall
give to any person, other than the Company, the Pass Through Trustee, each Owner
Lessor and each Lease Indenture Trustee, and their respective successors, and
the Holders of Certificates, any benefit or any legal or equitable right, remedy
or claim under this Pass Through Trust Agreement.

      Section 12.10. Counterparts. This Pass Through Trust Agreement may be
executed by the parties hereto in separate counterparts, each of which when so
executed and delivered shall be an original, but all such counterparts shall
together constitute but one and the same instrument.

      Section 12.11. Headings and Table of Contents. The headings of the
sections of this Pass Through Trust Agreement and the Table of Contents are
inserted for purposes of convenience only and shall not be construed to affect
the meaning or construction of any of the provisions hereof.

      Section 12.12. Further Assurances. Each party hereto will promptly and
duly execute and deliver such further documents and assurances for and take such
further action reasonably requested by the other party, all as may be reasonably
necessary to carry out more effectively the intent and purpose of this Pass
Through Trust Agreement.

      Section 12.13. Effectiveness. This Pass Through Trust Agreement has been
dated as of the date first above written for convenience only. This Pass Through
Trust Agreement shall be


                                       44
<PAGE>   50
effective on July 13, 2000, the date of execution and delivery by the Company
and the Pass Through Trustee.

      Section 12.14. Statement of Intent. It is intended that, if the Pass
Through Trust were ever to be classified as a partnership for Federal income tax
purposes, that the Pass Through Trust be excluded from the application of
Subchapter K of the Internal Revenue Code, in accordance with Treasury
Regulation 1.761-2(b)(2)(ii).


                                       45
<PAGE>   51
            IN WITNESS WHEREOF, the Company and the Pass Through Trustee have
caused this Pass Through Trust Agreement to be duly executed and delivered by
their respective officers thereunto duly authorized.




                                      PPL MONTANA, LLC

                                      By:  /s/ Paul A. Farr
                                          ---------------------------------
                                          Name:  Paul A. Farr
                                          Title: Vice President



                                      THE CHASE MANHATTAN BANK,
                                      as Pass Through Trustee


                                      By:  /s/ Annette M. Marsula
                                          ---------------------------------
                                          Name:  Annette M. Marsula
                                          Title: Vice President
<PAGE>   52
                                                                      SCHEDULE 1


                            Participation Agreements

            The Participation Agreements providing for Lease Transactions to be
financed by the purchase of Lessor Notes hereunder, and the parties thereto, are
as follows:

-     Participation Agreement (NC 1/2), dated as of July 13, 2000, among PPL
      Montana, LLC, a Delaware limited liability company, Montana OL1 LLC, a
      Delaware limited liability company, Wilmington Trust Company, a Delaware
      banking corporation, not in its individual capacity, except as expressly
      provided therein, but solely as Lessor Manager, Montana OP1 LLC, a
      Delaware limited liability company, The Chase Manhattan Bank, a New York
      banking corporation, not in its individual capacity, but solely as trustee
      under the Lease Indenture and The Chase Manhattan Bank, a New York banking
      corporation, not in its individual capacity, but solely as trustee under
      the Pass Through Trust Agreement.

-     Participation Agreement (NC 3), dated as of July 13, 2000, among PPL
      Montana, LLC, a Delaware limited liability company, Montana OL1 LLC, a
      Delaware limited liability company, Wilmington Trust Company, a Delaware
      banking corporation, not in its individual capacity, except as expressly
      provided therein, but solely as Lessor Manager, Montana OP1 LLC, a
      Delaware limited liability company, The Chase Manhattan Bank, a New York
      banking corporation, not in its individual capacity, but solely as trustee
      under the Lease Indenture and The Chase Manhattan Bank, a New York banking
      corporation, not in its individual capacity, but solely as trustee under
      the Pass Through Trust Agreement.

-     Participation Agreement (BA1/2), dated as of July 13, 2000, among PPL
      Montana, LLC, a Delaware limited liability company, Montana OL3 LLC, a
      Delaware limited liability company, Wilmington Trust Company, a Delaware
      banking corporation, not in its individual capacity, except as expressly
      provided therein, but solely as Lessor Manager, Montana OP3 LLC, a
      Delaware limited liability company, The Chase Manhattan Bank, a New York
      banking corporation, not in its individual capacity, but solely as trustee
      under the Lease Indenture and The Chase Manhattan Bank a New York banking
      corporation, not in its individual capacity, except as expressly provided
      therein, but solely as trustee under the Pass Through Trust Agreements.

-     Participation Agreement (BA3), dated as of July 13, 2000, among PPL
      Montana, LLC, a Delaware limited liability company, Montana OL4 LLC, a
      Delaware limited liability company, Wilmington Trust Company, a Delaware
      banking corporation, not in its individual capacity, except as expressly
      provided therein, but solely as Lessor Manager, Montana OP4 LLC, a
      Delaware limited liability company, The Chase Manhattan Bank, a New York
      banking corporation, not in its individual capacity, but solely as trustee
      under the Lease Indenture and The Chase Manhattan Bank, a New York banking
      corporation, not in its individual capacity, but solely as trustee under
      the Pass Through Trust Agreements.


                                    SCH 1-1
<PAGE>   53
                                                                       EXHIBIT A


                              FORM OF CERTIFICATE

              [LEGEND IF CERTIFICATE IS A RESTRICTED CERTIFICATE]

      THIS CERTIFICATE HAS NOT BEEN REGISTERED UNDER THE U.S. SECURITIES ACT OF
1933, AS AMENDED (THE "SECURITIES ACT"), AND, ACCORDINGLY, MAY NOT BE OFFERED OR
SOLD WITHIN THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR BENEFIT OF, U.S.
PERSONS EXCEPT AS SET FORTH IN THE FOLLOWING SENTENCE. BY ITS ACQUISITION
HEREOF, THE HOLDER (1) REPRESENTS THAT (A) IT IS A "QUALIFIED INSTITUTIONAL
BUYER" (AS DEFINED IN RULE 144A UNDER THE SECURITIES ACT) OR (B) IT IS AN
INSTITUTION WHICH IS AN "ACCREDITED INVESTOR" (AS DEFINED IN RULE 501(a)(l),
(2), (3) OR (7) OF REGULATION D UNDER THE SECURITIES ACT) (AN "INSTITUTIONAL
ACCREDITED INVESTOR") OR (C) IT IS NOT A U.S. PERSON AND IS ACQUIRING THIS
CERTIFICATE IN AN OFFSHORE TRANSACTION IN COMPLIANCE WITH REGULATION S UNDER THE
SECURITIES ACT, (2) AGREES THAT IT WILL NOT, WITHIN THE TIME PERIOD REFERRED TO
IN RULE 144(k) UNDER THE SECURITIES ACT, RESELL OR OTHERWISE TRANSFER THIS
CERTIFICATE EXCEPT (A) TO THE COMPANY OR ANY SUBSIDIARY THEREOF, (B) TO A
QUALIFIED INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE 144A UNDER THE SECURITIES
ACT, (C) INSIDE THE UNITED STATES TO AN INSTITUTIONAL ACCREDITED INVESTOR THAT,
PRIOR TO SUCH TRANSFER, FURNISHES TO THE PASS THROUGH TRUSTEE A SIGNED LETTER
CONTAINING CERTAIN REPRESENTATIONS AND AGREEMENTS RELATING TO THE RESTRICTIONS
ON TRANSFER OF THIS CERTIFICATE (THE FORM OF WHICH LETTER CAN BE OBTAINED FROM
THE PASS THROUGH TRUSTEE) [AND, IF SUCH TRANSFER IS IN RESPECT OF AN AGGREGATE
VALUE AT THE TIME OF TRANSFER OF CERTIFICATES OF LESS THAN $100,000, AN OPINION
OF COUNSEL ACCEPTABLE TO THE COMPANY THAT SUCH TRANSFER IS IN COMPLIANCE WITH
THE SECURITIES ACT], (D) OUTSIDE THE UNITED STATES IN AN OFFSHORE TRANSACTION IN
COMPLIANCE WITH RULE 904 UNDER THE SECURITIES ACT, (E) PURSUANT TO THE EXEMPTION
FROM REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES ACT (IF AVAILABLE),
OR (F) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT,
AND (3) AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM THIS CERTIFICATE IS
TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND. IN CONNECTION
WITH ANY TRANSFER OF THIS CERTIFICATE WITHIN THE TIME PERIOD REFERRED TO ABOVE,
THE HOLDER MUST CHECK THE APPROPRIATE BOX SET FORTH ON THE REVERSE HEREOF
RELATING TO THE MANNER OF SUCH TRANSFER AND SUBMIT THIS CERTIFICATE TO THE PASS
THROUGH TRUSTEE. AS USED HEREIN, THE TERMS "OFFSHORE TRANSACTION,"


                                    EXH A-1
<PAGE>   54
"UNITED STATES" AND "U.S. PERSON" HAVE THE MEANINGS GIVEN TO THEM BY REGULATION
S UNDER THE SECURITIES ACT. THE PASS THROUGH TRUST AGREEMENT CONTAINS A
PROVISION REQUIRING THE PASS THROUGH TRUSTEE TO REFUSE TO REGISTER ANY TRANSFER
OF THIS CERTIFICATE IN VIOLATION OF THE FOREGOING RESTRICTIONS.

            BY ITS ACQUISITION OF ANY CERTIFICATE, THE HOLDER THEREOF WILL BE
DEEMED TO HAVE REPRESENTED AND WARRANTED, ON EACH DAY FROM THE DATE ON WHICH THE
HOLDER ACQUIRES THE CERTIFICATE THROUGH AND INCLUDING THE DATE ON WHICH THE
HOLDER DISPOSES OF ITS INTEREST IN SUCH CERTIFICATE, EITHER THAT (A) IT IS NOT A
PLAN SUBJECT TO THE EMPLOYEE RETIREMENT INCOME SECURITY ACT OF 1974, AS AMENDED
("ERISA"), OR OTHER PLAN, AN ENTITY WHOSE UNDERLYING ASSETS INCLUDE THE ASSETS
OF ANY PLAN SUBJECT TO ERISA OR OTHER PLAN, OR A GOVERNMENTAL PLAN WHICH IS
SUBJECT TO ANY FEDERAL, STATE OR LOCAL LAW THAT IS SUBSTANTIALLY SIMILAR TO THE
PROVISIONS OF SECTION 406 OF ERISA OR SECTION 4975 OF THE INTERNAL REVENUE CODE
OF 1986, AS AMENDED (THE "CODE"), OR (B) ITS PURCHASE, HOLDING AND DISPOSITION
OF SUCH CERTIFICATE WILL NOT RESULT IN A PROHIBITED TRANSACTION UNDER SECTION
406 OF ERISA OR SECTION 4975 OF THE CODE (OR, IN THE CASE OF A GOVERNMENTAL
PLAN, ANY SUBSTANTIALLY SIMILAR FEDERAL, STATE OR LOCAL LAW) FOR WHICH AN
EXEMPTION IS NOT AVAILABLE, ALL THE CONDITIONS OF WHICH ARE SATISFIED.


                                    EXH A-2
<PAGE>   55
                        COLSTRIP 2000 PASS THROUGH TRUST

                               8.903% Pass Through
                                   Certificate

                                     CUSIP:

                     Final Distribution Date: July 20, 2020

             evidencing a fractional undivided interest in a trust,
             the property of which includes certain notes secured by
             certain property leased to PPL Montana, LLC.

Certificate No._______              $[___________] Fractional Undivided Interest

            THIS CERTIFIES THAT _________________, for value received, is the
registered owner of a $______________ (__________ dollars) Fractional Undivided
Interest in the Colstrip 2000 Pass Through Trust (the "Pass Through Trust")
created pursuant to a Pass Through Trust Agreement, dated as of July 13, 2000
(the "Agreement") between PPL Montana, LLC, a Delaware limited liability company
(the "Company"), and The Chase Manhattan Bank, as trustee (the "Pass Through
Trustee"), a summary of certain of the pertinent provisions of which is set
forth below. To the extent not otherwise defined herein, the capitalized terms
used herein have the meanings assigned to them in the Agreement. This
Certificate is one of the duly authorized Certificates designated as "8.903%
Pass Through Certificates" (herein called the "Certificates"). This Certificate
is issued under and is subject to the terms, provisions and conditions of the
Agreement, to which Agreement the Holder of this Certificate by virtue of the
acceptance hereof assents and by which such Holder is bound. The property of the
Pass Through Trust includes certain Lessor Notes (the "Trust Property"). The
Lessor Notes are secured by a security interest in certain undivided interests
in the Facility, and liability thereunder is limited to the income and proceeds
of such security.

            Subject to and in accordance with the terms of the Agreement, from
funds then available to the Pass Through Trustee, there will be distributed on
each January 2 and July 2 (a "Distribution Date"), commencing on January 2,
2001, to the person in whose name this Certificate is registered at the close of
business on the day of the month which is fifteen days preceding the
Distribution Date, an amount in respect of the Scheduled Payments on the Lessor
Notes due on such Distribution Date, the receipt of which has been confirmed by
the Pass Through Trustee, equal to the product of the percentage interest in the
Pass Through Trust evidenced by this Certificate and an amount equal to the sum
of such Scheduled Payments. Subject to and in accordance with the terms of the
Agreement, in the event that Special Payments on the Lessor Notes are received
by the Pass Through Trustee, from funds then available to the Pass Through
Trustee, there shall be distributed on the applicable Special Distribution Date,
to the Person in whose name this Certificate is registered at the close of
business on the day of the month which is fifteen days preceding the Special
Distribution Date, an amount in respect of such Special Payments on the Lessor
Notes, the receipt of which has been confirmed by the Pass


                                    EXH A-3
<PAGE>   56
Through Trustee, equal to the product of the percentage interest in the Pass
Through Trust evidenced by this Certificate and an amount equal to the sum of
such Special Payments so received. The Special Distribution Date shall be
determined as provided in the Agreement. If a Distribution Date or Special
Distribution Date is not a Business Day, distribution shall be made on the
immediately following Business Day. The Pass Through Trustee shall mail notice
of each Special Payment and the Special Distribution Date therefor to the
Holders of the Certificates.

            Distributions on this Certificate will be made by the Pass Through
Trustee (i) if (A) The Depository Trust Company ("DTC") is the Certificateholder
of record of this Certificate, or (B) a Certificateholder holds a Certificate or
Certificates in an aggregate amount greater than $10,000,000, or (C) a
Certificateholder holds a Certificate or Certificates in an aggregate amount
greater than $1,000,000 and so requests to the Pass Through Trustee, by wire
transfer in immediately available funds to an account maintained by such
Certificateholder with a bank, or (ii) if none of the above apply, by check
mailed to such Certificateholder at the address appearing in the Register,
without the presentation or surrender of this Certificate or the making of any
notation hereon. Except as otherwise provided in the Agreement and
notwithstanding the above, the final distribution on this Certificate will be
made after notice mailed by the Pass Through Trustee of the pendency of such
distribution and only upon presentation and surrender of this Certificate at the
office or agency of the Pass Through Trustee specified in such notice.

            [Unless this Certificate is presented by an authorized
representative of DTC to the Company or its agent for registration of transfer,
exchange or payment, and any Certificate issued is registered in the name of
Cede & Co., or in such other name as is requested by an authorized
representative of DTC (and any payment is made to Cede & Co., or to such other
entity as is requested by an authorized representative of DTC), ANY TRANSFER,
PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS
WRONGFUL in as much as the registered owner hereof, Cede & Co., has an interest
herein.]*

            Each Person who acquires or accepts this Certificate or an interest
herein will be deemed by such acquisition or acceptance to have represented and
warranted that either: (i) no Plan assets have been used to purchase this
Certificate or an interest herein or (ii) the purchase and holding of this
Certificate or interest herein are either exempt from the prohibited transaction
restrictions of ERISA and the Code pursuant to one or more prohibited
transaction statutory or administrative exemptions or do not constitute a
prohibited transaction under such restrictions of ERISA and the Code.

            This Certificate shall be governed by and construed in accordance
with the law of the State of New York.

            Reference is hereby made to the further provisions of this
Certificate set forth on the reverse hereof, which further provisions shall for
all purposes have the same effect as if set forth at this place.



----------
* This legend to appear on Book-Entry  Certificates  to be deposited  with The
Depository Trust Company.


                                    EXH A-4
<PAGE>   57
            Unless the certificate of authentication hereon has been executed by
the Pass Through Trustee, by manual signature, this Certificate shall not be
entitled to any benefit under the Agreement or be valid for any purpose.

            IN WITNESS WHEREOF, the Pass Through Trustee has caused this
Certificate to be duly executed.


                                    COLSTRIP 2000 PASS THROUGH TRUST



                                    By:The Chase Manhattan Bank,
                                       as Pass Through Trustee



                                    By: ____________________________________
                                        Name:
                                        Title:


                                    EXH A-5
<PAGE>   58
                            [Reverse Of Certificate]

            The Certificates do not represent a direct obligation of, or an
obligation guaranteed by, or an interest in, the Company, the Pass Through
Company or the Pass Through Trustee or any affiliate thereof. The Certificates
are limited in right of payment, all as more specifically set forth in the
Agreement. All payments or distributions made to Certificateholders under the
Agreement shall be made only from the Trust Property and only to the extent that
the Pass Through Trustee shall have received sufficient income or proceeds from
the Trust Property to make such payments in accordance with the terms of the
Agreement. Each Holder of this Certificate, by its acceptance hereof, agrees
that it will look solely to the income and proceeds from the Trust Property to
the extent available for distribution to such Holder as provided in the
Agreement. This Certificate does not purport to summarize the Agreement and
reference is made to the Agreement for information with respect to the
interests, rights, benefits, obligations, proceeds and duties evidenced hereby.
A copy of the Agreement may be examined during normal business hours at the
principal office of the Pass Through Trustee, and at such other places, if any,
designated by the Pass Through Trustee, by any Certificateholder upon request.

            The Agreement permits, with certain exceptions therein provided, the
amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Certificateholders under the Agreement at any time
by the Company and the Pass Through Trustee with the consent of the Holders of
Certificates evidencing Fractional Undivided Interests aggregating not less than
a majority in interest of the Fractional Undivided Interests evidenced by all
Certificates at the time Outstanding. Any such consent by the Holder of this
Certificate shall be conclusive and binding on such Holder and upon all future
Holders of this Certificate and of any Certificate issued upon the transfer
hereof or in exchange hereof or in lieu hereof whether or not notation of such
consent is made upon this Certificate. The Agreement also permits the amendment
thereof, in certain limited circumstances, without the consent of the Holders of
any of the Certificates.

            As provided in the Agreement and subject to certain limitations
therein set forth, the transfer of this Certificate is registrable in the
Register upon surrender of this Certificate for registration of transfer at the
offices or agencies maintained by the Pass Through Trustee in its capacity as
Registrar, or by any successor Registrar, in the Borough of Manhattan, the City
of New York, duly endorsed or accompanied by a written instrument of transfer in
form satisfactory to the Pass Through Trustee and the Registrar duly executed by
the Holder hereof or such Holder's attorney duly authorized in writing, and
thereupon one or more new Certificates of authorized denominations evidencing
the same aggregate Fractional Undivided Interest in the Pass Through Trust will
be issued to the designated transferee or transferees.

            The Certificates are issuable only as registered Certificates
without coupons in minimum denominations of $100,000 Fractional Undivided
Interest and any integral multiples of $1,000 in excess thereof. As provided in
the Agreement and subject to certain limitations therein set forth, Certificates
are exchangeable for new Certificates of authorized denominations evidencing the
same aggregate Fractional Undivided Interest in the Pass Through Trust, as
requested by the Holder surrendering the same.


                                    EXH A-6
<PAGE>   59
            No service charge will be made for any such registration of transfer
or exchange, but the Pass Through Trustee shall require payment of an amount
sufficient to cover any tax or charge payable in connection therewith.

            The Pass Through Trustee, the Company, the Owner Lessor, the
Registrar and any agent of the Pass Through Trustee or the Registrar may treat
the person in whose name this Certificate is registered as the owner hereof for
all purposes, and neither the Pass Through Trustee, the Company, the Owner
Lessor, the Registrar nor any such agent shall be affected by any notice to the
contrary.

            The obligations and responsibilities created by the Agreement and
the Pass Through Trust created thereby shall terminate upon the distribution to
Certificateholders of all amounts required to be distributed to them pursuant to
the Agreement and the disposition of all property held as part of the Trust
Property.


                                    EXH A-7
<PAGE>   60
                                                                       EXHIBIT B

          FORM OF PASS THROUGH TRUSTEE'S CERTIFICATE OF AUTHENTICATION

 This is one of the Certificates referred to in the within-mentioned Agreement.




                                    THE CHASE MANHATTAN BANK,
                                    as Pass Through Trustee



                                    By: ____________________________________
                                        Name:
                                        Title:





                                    EXH B-1
<PAGE>   61
                                                                       EXHIBIT C


                          FORM OF TRANSFER CERTIFICATE

                                   CERTIFICATE

                        COLSTRIP 2000 PASS THROUGH TRUST

                            PASS THROUGH CERTIFICATES

            This is to certify that as of the date hereof with respect to
$__________ (__________ dollars) Fractional Undivided Interest of the
above-captioned securities presented or surrendered on the date hereof (the
"Surrendered Certificates") for registration of transfer, or for exchange where
the securities issuable upon such exchange are to be registered in a name other
than that of the undersigned Holder (each such transaction being a "transfer"),
the undersigned Holder (as defined in the Pass Through Trust Agreement)
certifies that the transfer of Surrendered Certificates associated with such
transfer complies with the restrictive legend set forth on the face of the
Surrendered Certificates for the reason checked below:


| |   Transfer to Colstrip 2000 Pass Through Trust

| |   Transfer inside the United States to a Qualified Institutional Buyer in
      compliance with Rule 144A under the Securities Act.

| |   Transfer pursuant to an exemption from registration provided by Rule 144
      under the Securities Act (if available).

| |   Transfer pursuant to an effective registration statement under the
      Securities Act.

| |   Transfer outside the United States in compliance with Rule 904 of the
      Securities Act.

| |   Transfer inside the United States to an Institutional Accredited Investor
      that has previously furnished to the Pass Through Trustee a signed letter
      containing certain representations and agreements relating to restrictions
      on transfer and if such transfer is in respect of an aggregate Fractional
      Undivided Interest of less than $100,000, an opinion of counsel acceptable
      to the Company that such transfer is in compliance with the Securities
      Act.



                                [Name of Holder]

                                ----------------


Dated: _____________, ______(*)


* To be dated the date of presentation or surrender


                                    EXH C-1
<PAGE>   62
                                                                       EXHIBIT D


                          FORM OF PURCHASE LETTER FOR
                       INSTITUTIONAL ACCREDITED INVESTORS


CHASE SECURITIES INC.
CREDIT SUISSE FIRST BOSTON
VBS WARBURG LLC
TD SECURITIES(USA) INC.
As Initial Purchasers in connection
with the Offering Memorandum referred
to below

c/o Chase Securities
270 Park Avenue
New York, New York 10017

Ladies and Gentlemen:

            In connection with our proposed purchase of Pass Through
Certificates, (the "Certificates") evidencing a fractional undivided interest in
a trust, the property of which consists of certain notes secured by certain
property leased to PPL Montana, LLC (the "Company"), we confirm that:

            1. We have received a copy of the Offering Memorandum (the "Offering
      Memorandum") relating to the Certificates and such other information as we
      deem necessary in order to make our investment decision. We acknowledge
      that we have read and agree to the matters stated under the captions
      "Notice to Investors" and "Plan of Distribution" in such Offering
      Memorandum, and the restrictions on duplication and circulation of such
      Offering Memorandum.

            2. We understand that any subsequent transfer of the Certificates is
      subject to certain restrictions and conditions set forth in the Pass
      Through Trust Agreements (the "Pass Through Trust Agreement") relating to
      the Certificates and conditions set forth under "Notice to Investors" and
      "Plan of Distribution" and we agree to be bound by, and not to resell,
      pledge or otherwise transfer the Certificates except in compliance with
      such restrictions and conditions and the Securities Act of 1933, as
      amended (the "Securities Act").

            3. We understand that the offer and sale of the Certificates has not
      been registered under the Securities Act, and that the Certificates may
      not be offered or sold except as permitted in the following sentence. We
      agree, on our own behalf and on behalf of any accounts for which we are
      acting as hereinafter stated, that if we should sell any


                                    EXH D-1
<PAGE>   63
      Certificates within the time period referred to in Rule 144(k) of the
      Securities Act, we will do so only (A) to the Company or any subsidiary
      thereof, (B) in accordance with Rule 144A under the Securities Act to a
      "qualified institutional buyer" (as defined therein), (C) to an
      institutional "accredited investor" (as defined below) that, prior to such
      transfer, furnishes to the Pass Through Trustee under the Pass Through
      Trust Agreement, a signed letter containing certain representations and
      agreements relating to the restrictions on transfer of the Certificates
      (the form of which letter can be obtained from the Pass Through Trustee)
      and, if such transfer is in respect of an aggregate principal amount at
      the time of transfer of Certificates of less than $100,000, an opinion of
      counsel acceptable to the Company that such transfer is in compliance with
      the Securities Act, (D) outside the United States in accordance with Rule
      904 of Regulation S under the Securities Act, (E) pursuant to the
      exemption from registration provided by Rule 144 under the Securities Act
      (if available), or (F) pursuant to an effective registration statement
      under the Securities Act, and we further agree to provide to any person
      purchasing any of the Certificates from us a notice advising such
      purchaser that resales of the Certificates are restricted as stated
      herein.

            4. We are an institutional "accredited investor" (as defined in Rule
      501(a)(1), (2), (3) or (7) of Regulation D under the Securities Act) and
      have such knowledge and experience in financial and business matters as to
      be capable of evaluating the merits and risks of our investment in the
      Certificates, and we and any accounts for which we are acting are each
      able to bear the economic risk of our or its investment.

            5. We are acquiring the Certificates purchased by us for our own
      account or for one or more accounts (each of which is an institutional
      "accredited investor") as to each of which we exercise sole investment
      discretion.

            6. We are not acquiring the Certificates with a view to distribution
      thereof or with any present intention of offering or selling any
      Certificates, except as permitted above; provided, that the disposition of
      our property and property of any accounts for which we are acting as
      fiduciary will remain at all times within our control.


                                    EXH D-2
<PAGE>   64
            You, the Company and the Pass Through Trustee are entitled to rely
on this letter and are irrevocably authorized to produce this letter or a copy
hereof to any interested party in any administrative or legal proceedings or
official inquiry with respect to the matters covered hereby.


                                    Very truly yours,




                                    By: ________________________

                                        Name:
                                        Title:
                                        Date:


                                    EXH D-3