<PAGE>   1
                                                                   Exhibit 10.23

                                                                  EXECUTION COPY

                         OMNIBUS VOTING RIGHTS AGREEMENT
                                    (BA/NC-3)

                            Dated as of July 20, 2000

                                      among

                                PPL MONTANA, LLC,

                                MONTANA OL1 LLC,

                                MONTANA OL4 LLC,

                            THE CHASE MANHATTAN BANK,
 as trustee under the Indenture of Trust, Mortgage and Security Agreement (NC3),
                 dated as of July 20, 2000 with Montana OL1 LLC

                                       and

                            THE CHASE MANHATTAN BANK,
 as trustee under the Indenture of Trust, Mortgage and Security Agreement (BA3),
                 dated as of July 20, 2000 with Montana OL4 LLC



                           COLSTRIP GENERATING UNIT 3
                          AND RELATED COMMON FACILITIES
<PAGE>   2
                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                        PAGE
                                                                        ----
<S>                                                                     <C>
SECTION 1. DEFINITIONS; INTERPRETATION OF THIS OMNIBUS VOTING
           AGREEMENT................................................      2

SECTION 2. EXERCISE OF RIGHTS UNDER VOTE SHARING AGREEMENT..........      3

SECTION 3. RIGHTS OF INDENTURE TRUSTEES UPON LEASE EVENT OF
           DEFAULT .................................................      3

SECTION 4. MISCELLANEOUS............................................      3

   Section 4.1. Amendments and Waivers; Termination ................      3

   Section 4.2. Notices ............................................      4

   Section 4.3. Successors and Assigns .............................      5

   Section 4.4. Measuring Life .....................................      5

   Section 4.5. Governing Law ......................................      6

   Section 4.6. Severability .......................................      6

   Section 4.7. Counterparts .......................................      6

   Section 4.8. Headings and Table of Contents .....................      6

   Section 4.9. Limitation of Liability ............................      6

   Section 4.10.Effectiveness ......................................      7

   Section 4.11.No Partnership, Etc ................................      7
</TABLE>


                                       i
<PAGE>   3
                         OMNIBUS VOTING RIGHTS AGREEMENT

                                    (BA/NC-3)

      This OMNIBUS VOTING RIGHTS AGREEMENT (BA/NC-3), dated as of July 20, 2000
(this "Omnibus Voting Agreement"), among (i) PPL MONTANA, LLC, a Delaware
limited liability company ("PPL Montana"), (ii) MONTANA OL1 LLC, a Delaware
limited liability company (the "Owner Lessor (1)"), (iii) MONTANA OL4 LLC, a
Delaware limited liability company (the "Owner Lessor (4)" and, together with
the Owner Lessor (1), the "Owner Lessors"), (iv) THE CHASE MANHATTAN BANK, a
banking corporation organized and existing under the laws of the State of New
York, not in its individual capacity, but solely as trustee under the Indenture
of Trust, Mortgage and Security Agreement (NC3), dated as of July 20, 2000
("Lease Indenture (2)") with the Owner Lessor (1) (in such capacity, the "Lease
Indenture Trustee (2)", and (v) THE CHASE MANHATTAN BANK, a banking corporation
organized and existing under the laws of the State of New York, not in its
individual capacity, but solely as trustee under the Indenture of Trust Mortgage
and Security Agreement (BA3), dated as of July 20, 2000 ("Lease Indenture (4)")
with the Owner Lessor (4), (in such capacity, the "Lease Indenture Trustee (4)",
and, together with the Lease Indenture Trustee (2), the "Lease Indenture
Trustees").

                              W I T N E S S E T H:

      WHEREAS, the rights and obligations as tenants-in-common of the co-owners
of Units 3 and 4 and the Common Facilities 3-4 are governed by the Ownership
Agreement 3-4; and the rights and obligations as tenants-in-common of the
co-owners of the Common Facilities 1-2-3-4 are governed by the Common Facilities
Agreement;

      WHEREAS, in connection with the purchase by PPL Montana of Unit 3 from The
Montana Power Company ("MPC"), PPL Montana and MPC entered into a Project
Committee Vote Sharing Agreement, entered into as of December 17, 1999 (the
"Vote Sharing Agreement") in accordance with which PPL Montana, as "Owner" of
Unit 3, and MPC, as "Project User" of Unit 4, agreed to share the right to
direct the vote of one member of the Project Committee created pursuant to
Section 17 of the Ownership Agreement 3-4 (such vote of such member of the
Project Committee shared by PPL Montana and MPC pursuant to the Vote Sharing
Agreement hereinafter called the "Shared Vote");

      WHEREAS, simultaneously herewith, PPL Montana has conveyed to each Owner
Lessor such Owner Lessor's respective Undivided Interest with respect to Unit 3
pursuant to each Owner Lessor's respective Bill of Sale, and has leased to each
Owner Lessor such Owner Lessor's respective Ground Interest with respect to Unit
3 pursuant to such Owner Lessor's respective Site Lease and Sublease;

      WHEREAS, each Owner Lessor will lease to PPL Montana such Owner Lessor's
respective Undivided Interest with respect to Unit 3 pursuant to such Owner
Lessor's respective Facility Lease, and will sublease to PPL Montana such Owner
Lessor's respective Ground Interest with respect to Unit 3 pursuant to such
Owner Lessor's respective Site Lease and Sublease, in each case, for such Owner
Lessor's respective Facility Lease Term;
<PAGE>   4
      WHEREAS, pursuant to separate Assignment and Reassignment Agreements, each
dated as of July 20, 2000 between PPL Montana, LLC and each Owner Lessor
(collectively, the "Assignment and Reassignments"), (i) PPL Montana shall be,
and have the rights of, a "Project User" to the extent of each Undivided
Interest in Unit 3 and each Owner Lessor shall be, and have the rights of, an
"Owner" to the extent of its Undivided Interest in Unit 3, (ii) PPL Montana
assigned to the applicable Owner Lessor all of PPL Montana's right, title and
interest as "Owner" under the Common Facilities Agreement related to such Owner
Lessor's Undivided Interest with respect to Unit 3, and (iii) each Owner Lessor
reassigned all of such Owner Lessor's right, title, and interest with respect to
Unit 3 under the Common Facilities Agreement assigned to it by PPL Montana back
to PPL Montana for a term equal to its Facility Lease Term (unless terminated
earlier pursuant to the terms of its Assignment and Reassignment);

      WHEREAS, pursuant to the Assignment and Reassignment Agreement between PPL
Montana and Owner Lessor (4), PPL Montana has assigned its rights in the Vote
Sharing Agreement to Owner Lessor (4) and Owner Lessor (4) has reassigned such
rights back to PPL Montana;

      WHEREAS, each Assignment and Reassignment contemplates that the
appointment of the representative to the Owner's Committee under the Ownership
Agreement 3-4 on behalf of each Undivided Interest with respect to Unit 3
assigned to the applicable Owner Lessor pursuant to such Assignment and
Reassignment shall be made in accordance with this Omnibus Voting Agreement; and

      WHEREAS, pursuant to this Omnibus Voting Agreement and the terms hereof,
the Owner Lessor (1), the Owner Lessor (4), the Lease Indenture Trustee (2), the
Lease Indenture Trustee (4), and PPL Montana will establish the terms under
which the exercise of the Shared Vote in accordance with the Vote Sharing
Agreement and Ownership Agreement 3-4 in respect of the interests of each Owner
Lessor in Unit 3 will be exercised, and (ii) the Owner Lessor (1), the Owner
Lessor (4) and PPL Montana will agree with the Lease Indenture Trustee (2) and
the Lease Indenture Trustee (4) that the Lease Indenture Trustee (2) or the
Lease Indenture Trustee (4) may exercise such rights in certain circumstances.

      NOW, THEREFORE, in consideration of the foregoing premises, the mutual
agreements herein contained and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

SECTION 1. DEFINITIONS; INTERPRETATION OF THIS OMNIBUS VOTING AGREEMENT

      The capitalized terms used in this Omnibus Voting Agreement, including the
foregoing recitals, and not otherwise defined herein shall have the respective
meanings specified in Appendix A to the Participation Agreements referred to in
the Assignment and Reassignments. The general provisions of each Appendix A
shall apply to terms used in this Omnibus Voting Agreement and specifically
defined herein.

                                       2
<PAGE>   5
SECTION 2. EXERCISE OF RIGHTS UNDER VOTE SHARING AGREEMENT.

      (a) Owner Lessor (1), Owner Lessor (4), and PPL Montana agree that the
exercise of all of PPL Montana's rights under the Vote Sharing Agreement,
including the appointment of the representative to the Project Committee
pursuant to Section 17 of the Ownership Agreement 3-4 shall be appointed by the
owner or owners of the Undivided Interests with respect to Unit 3 who own more
than 50% in the aggregate of such Undivided Interests. For purposes of this
Section 2, PPL Montana shall be deemed to be the owner of any Undivided Interest
for which the Lessor Possession Date (as defined in the relevant Assignment and
Reassignment) shall not have occurred.

      (b) The parties hereto appoint (i) PPL Montana unless and until a Lessor
Possession Date shall have occurred under the Facility Lease with Owner Lessor
(4), and (ii) thereafter Owner Lessor (4) or, if an Indenture Event of Default
shall have occurred and be continuing under the Lease Indenture (4), Indenture
Trustee (4), to act under the Vote Sharing Agreement, in either case (i) or
(ii), as directed pursuant to Section 2(a) and 3.

SECTION 3. RIGHTS OF INDENTURE TRUSTEES UPON LEASE EVENT OF DEFAULT.

      Notwithstanding any other provision of this Omnibus Voting Agreement or
any other Operative Document to the contrary, each of the parties to this
Omnibus Voting Agreement agrees that, upon the occurrence and during the
continuance of a Lease Event of Default under the Facility Lease of either Owner
Lessor, the Lease Indenture Trustee which is a party to the Lease Indenture in
respect of which the Lease Event of Default shall have occurred and is
continuing, shall, so long as the Lien of the respective Lease Indenture shall
not have been terminated or discharged, have the right, to the exclusion of PPL
Montana and either Owner Lessor, to direct the parties appointed pursuant to
Section 2(b) in the exercise of all of PPL Montana's rights under the Vote
Sharing Agreement with respect to the Shared Vote, including, to the extent
permitted by the Vote Sharing Agreement, appointment of the representative to
the Owner's Committee and the right to direct all such representative's actions
and votes thereunder. Upon the occurrence and during the continuance of a Lease
Event of Default under both Facility Leases, both Lease Indenture Trustees
shall, so long as the Lien of their respective Lease Indentures shall not have
been terminated or discharged, have the right to the exclusion of PPL Montana
and either Owner Lessor, to jointly direct the parties appointed pursuant to
Section 2(b) in the exercise of all of PPL Montana's rights under the Vote
Sharing Agreement with respect to the Shared Vote.

SECTION 4. MISCELLANEOUS

      Section 4.1. Amendments and Waivers; Termination. No term, covenant,
agreement or condition of this Omnibus Voting 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. Notwithstanding the foregoing, if the
Ownership Agreement 3-4 is amended or clarified so as to permit each Owner and
Project User (each as defined in the Ownership Agreement 3-4) and each direct or
subsequent transferee of either (including any lessee) the right to appoint a
separate

                                       3
<PAGE>   6
member to the Owner's Committee, this Agreement shall be terminated and be of no
further force and effect.

      Section 4.2. Notices. Unless otherwise expressly specified or permitted by
the terms hereof, all communications and notices provided for herein 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 each party hereto at its address set forth
below or, in the case of any such party hereto, at such other address as such
party may from time to time designate by written notice to the other parties
hereto:

      If to PPL Montana:

            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 Owner Lessor (1):

            Montana OL1 LLC
            c/o Wilmington Trust Company
            Rodney Square North
            1100 North Market Street
            Wilmington, Delaware 19890-0001
            Telephone No.:  (302) 651-1000
            Facsimile No.:  (302) 651-8882
            Attention: Corporate Trust Administration

      If to the Owner Lessor (4):

            Montana OL4 LLC
            c/o Wilmington Trust Company
            Rodney Square North
            1100 North Market Street
            Wilmington, Delaware 19890-0001
            Telephone No.:  (302) 651-1000
            Facsimile No.:  (302) 651-8882
            Attention: Corporate Trust Administration

                                       4
<PAGE>   7
      If to the Lease Indenture Trustee (2):

            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


      If to the Lease Indenture Trustee (4):

            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 4.3. Successors and Assigns. This Omnibus Voting 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. Except as expressly provided herein or
in the other Operative Documents (as defined in each respective Assignment and
Reassignment), no party hereto may assign its interests herein without the
consent of the other parties hereto. If any party hereto transfers or assigns
any of its Undivided Interest, then such party shall assign all of its rights
and obligations under this Omnibus Voting Agreement related to such transferred
or assigned interest to the proposed transferee or assignee. Any attempted or
purported transfer and assignment other than in accordance with this Section
shall be void and of no effect.

      Section 4.4. Measuring Life. If and to the extent that any of the rights
and privileges granted under this Omnibus Voting 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 interests in property or the suspension of the power
of alienation of property, then it is agreed that notwithstanding any other
provision of this Omnibus Voting 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 Facility
Lease 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 specific applicable period of
time expressed in this Omnibus Voting Agreement, whichever of (a) and (b) is
shorter.

                                       5
<PAGE>   8
      Section 4.5. Governing Law. This Omnibus Voting Agreement has been
delivered in the State of New York and shall be in all respects governed by and
construed in accordance with the laws of the State of New York including all
matters of construction, validity and performance without giving effect to the
conflicts of laws provisions thereof except New York General Obligations Law
Section 5-1401.

      Section 4.6. Severability. If any provision hereof shall be invalid,
illegal or unenforceable under Applicable Law, the validity, legality and
enforceability of the remaining provisions hereof shall not be affected or
impaired thereby.

      Section 4.7. Counterparts. This Omnibus Voting Agreement may be executed
in any number of counterparts, each executed counterpart constituting an
original but all together only one agreement.

      Section 4.8. Headings and Table of Contents. The headings of the sections
of this Omnibus Voting 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 4.9. Limitation of Liability. (a) It is expressly understood and
agreed by the parties hereto that (a) this Omnibus Voting Agreement is executed
and delivered by Wilmington Trust Company ("Wilmington"), not individually or
personally but solely as Lessor Manager under the relevant LLC Agreement, in the
exercise of the powers and authority conferred and vested in it pursuant
thereto, (b) each of the undertakings and agreements herein made on the part of
each Owner Lessor are made and intended not as personal undertakings and
agreements by Wilmington but are made and intended for the purpose for binding
only an Owner Lessor, (c) nothing herein contained shall be construed as
creating any liability on Wilmington individually or personally, to perform any
covenant either expressed or implied contained herein, all such liability, if
any, being expressly waived by the parties hereto or by any Person claiming by,
through or under the parties hereto and (d) under no circumstances shall
Wilmington, be personally liable for the payment of any indebtedness or expenses
of either Owner Lessor or be liable for the breach or failure of any obligation,
representation, warranty or covenant made or undertaken by either Owner Lessor
under this Omnibus Voting Agreement.

      (b) It is expressly understood and agreed by the parties hereto that (a)
this Omnibus Voting Agreement is executed and delivered by The Chase Manhattan
Bank ("Chase"), not individually or personally but solely as Lease Indenture
Trustee under the relevant Lease Indenture, in the exercise of the powers and
authority conferred and vested in it pursuant thereto, (b) each of the
undertakings and agreements herein made in such capacity are made and intended
not as personal undertakings and agreements by Chase but are made and intended
in its capacity as Lease Indenture Trustee, (c) nothing herein contained shall
be construed as creating any liability on Chase individually or personally, to
perform any covenant either expressed or implied contained herein, all such
liability, if any, being expressly waived by the parties hereto or by any Person
claiming by, through or under the parties hereto, and (d) under no circumstances
shall Chase be personally liable for the payment of any indebtedness or expenses
in its capacity as Lease Indenture Trustee or be liable for the breach or
failure of any obligation,

                                       6
<PAGE>   9
representation, warranty or covenant made or undertaken in such capacity under
this Omnibus Voting Agreement.

      Section 4.10. Effectiveness. This Omnibus Voting Agreement has been dated
as of the date first above written for convenience only. This Omnibus Voting
Agreement shall become effective on July 20, 2000, the date of execution and
delivery by each of the parties hereto.

      Section 4.11. No Partnership, Etc. The parties hereto intend that nothing
contained in this Omnibus Voting Agreement shall be deemed or construed to
create a partnership, joint venture or other co-ownership arrangement by and
among any of them.

                                       7
<PAGE>   10
      IN WITNESS WHEREOF, the parties hereto have caused this Omnibus Voting
Agreement to be 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

                              MONTANA OL1 LLC

                              By: Wilmington Trust Company, not in its
                                  individual capacity but solely as Lessor
                                  Manager

                              By: /s/ James P. Lawler
                                  ---------------------------
                                  Name: James P. Lawler
                                  Title:Vice President

                              MONTANA OL4 LLC

                              By: Wilmington Trust Company, not in its
                                  individual capacity but solely as its
                                  Independent Manager

                              By: /s/ James P. Lawler
                                  ---------------------------
                                  Name:  James P. Lawler
                                  Title: Vice President

                              THE CHASE MANHATTAN BANK
                              not in its individual capacity, but solely as
                              Lease Indenture Trustee (1) under the Lease
                              Indenture (1)

                              By: /s/ Annette M. Marsula
                                  ---------------------------
                                  Name:  Annette M. Marsula
                                  Title: Vice President

                              THE CHASE MANHATTAN BANK,
                              not in its individual capacity, but solely as
                              Lease Indenture Trustee (4) under the Lease
                              Indenture (4)


                              By: /s/ Annette M. Marsula
                                  ---------------------------
                                  Name:  Annette M. Marsula
                                  Title: Vice President