<PAGE>

                                                                   Exhibit 10.4a

                                                                  Execution Copy


================================================================================


                          Shared Facilities Agreement
                                   (Roseton)


                            Dated as of May 8, 2001


                                    between


                            Dynegy Roseton, L.L.C.


                                      and
                                Roseton OL LLC



                             Roseton Units 1 and 2



--------------------------------------------------------------------------------
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                   Page
<S>                                                                               <C>
ARTICLE I    DEFINITIONS.........................................................   2
     SECTION 1.1     Definitions.................................................   2
     SECTION 1.2     Use of Definitions..........................................   3

ARTICLE II   EFFECTIVE DATE; TERM................................................   3
     SECTION 2.1     Effective Date of Agreement.................................   3
     SECTION 2.2     Term........................................................   4

ARTICLE III  SHARED FACILITIES...................................................   4
     SECTION 3.1     Use of Shared Facilities....................................   4
     SECTION 3.2     Ownership of Shared Facilities..............................   4
     SECTION 3.3     Operation and Maintenance of Shared Facilities..............   4
     SECTION 3.4     Insurance for Shared Facilities.............................   5
     SECTION 3.5     Non-Exclusive Right to Use, Control of Shared Facilities....   6
     SECTION 3.6     Force Majeure...............................................   6
     SECTION 3.7     Condemnation of Shared Facilities...........................   6
     SECTION 3.8     Survival of Rights in Shared Facilities.....................   6

ARTICLE IV   PAYMENT.............................................................   7
     SECTION 4.1     Payment.....................................................   7
     SECTION 4.2     Late Payments...............................................   7
     SECTION 4.3     Payment Default.............................................   8
     SECTION 4.4     Right of Setoff.............................................   8

ARTICLE V    MISCELLANEOUS.......................................................   8
     SECTION 5.1     Amendments and Waivers......................................   8
     SECTION 5.2     Notices.....................................................   8
     SECTION 5.3     Successors and Assigns......................................   9
     SECTION 5.4     Transfers and Assignments...................................   9
     SECTION 5.5     Governing Law...............................................  10
     SECTION 5.6     Severability................................................  10
     SECTION 5.7     Counterparts................................................  10
     SECTION 5.8     Headings and Table of Contents..............................  10
     SECTION 5.9     Further Assurances..........................................  10
     SECTION 5.10    Limitation of Liability.....................................  11
</TABLE>

                                      -i-
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                           Page
<S>                                                                        <C>
EXHIBIT A - Company Shared Facilities

EXHIBIT B - Owner Lessor Shared Facilities
</TABLE>

                                      -i-
<PAGE>

                          Shared Facilities Agreement
                                   (Roseton)

     THIS SHARED FACILITIES AGREEMENT (this "Agreement"), dated as of May 8,
                                             ---------
2001 is entered into between DYNEGY ROSETON, L.L.C., a Delaware limited
liability company (the "Company") and ROSETON OL LLC, a Delaware limited
                        -------
liability company (the "Owner Lessor").  The Owner Lessor and the Company are
                        ------------
referred to herein individually as a "Party" and collectively as the "Parties."
                                      -----                           -------

                             W I T N E S S E T H:
                             - - - - - - - - - -

     WHEREAS, pursuant to the Deed and the Bill of Sale, the Owner Lessor has
acquired the Facility from the Company, and concurrently leased the Facility to
the Company pursuant to the Facility Lease;

     WHEREAS, pursuant to the Site Lease, the Owner Lessor has leased the Ground
Interest from the Company, and concurrently leased the Ground Interest to the
Company pursuant to the Site Sublease;

     WHEREAS, the Owner Lessor desires to obtain from the Company the right to
use certain property and equipment located on the Facility Site or on the
Additional Facility Site and more fully described on Exhibit A hereto (the
"Company Shared Facilities"), together with certain related services, and the
 -------------------------
Company desires to obtain from the Owner Lessor the right to use, and to permit
any Additional Owner to use, certain property and equipment located on the
Facility Site and more fully described on Exhibit B hereto (the "Owner Lessor
                                                                 ------------
Shared Facilities"), together with certain related services, in each case which
-----------------
are used in common with the Company Owned Facilities and Owner Lessor Owned
Facilities (the Company Shared Facilities and the Owner Lessor Shared Facilities
being referred to herein collectively as the "Shared Facilities"), and each
                                              -----------------
Party hereto is willing to make available its interest in such property and
equipment and to provide such services to the other Party on the terms and
conditions provided herein; and

     WHEREAS, as a condition to the obligations of the Parties under the
Participation Agreement and the other Operative Documents, the Parties desire to
enter into this Agreement to establish their respective rights in the Shared
Facilities and the services relating to the operation and maintenance of the
Company Owned Facilities and the Owner Lessor Owned Facilities and the other
matters provided herein.

     NOW, THEREFORE, in consideration of the payments hereunder, the mutual
agreements contained herein, and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Parties hereto
agree as follows:
<PAGE>

                                   ARTICLE I

                                  DEFINITIONS

     SECTION 1.1 Definitions.  Unless the context hereof shall otherwise
require, capitalized terms used, including those in the recitals, and not
otherwise defined herein shall have the respective meanings set forth in
Appendix A to the Participation Agreement, dated as of May 1, 2001, among the
Company, the Owner Lessor, the Owner Participant named therein, Wilmington Trust
Company in the capacities referred to therein, and The Chase Manhattan Bank in
the capacities referred to therein. The general provisions of such Appendix A
shall apply to the terms used in this Agreement.

          "Additional Owner" shall have the meaning specified in the Site Lease.
           ----------------

          "Company Owned Facilities" shall mean (i) the electric generation
           ------------------------
     facilities and related assets owned by the Company or any of its Affiliates
     and not sold to the Owner Lessor that are located on the Facility Site,
     including but not limited to the Company Shared Facilities, and (ii) any
     Additional Facility at any time owned or operated by the Company or an
     Additional Owner on the Additional Facility Site or othewise.

          "Company Shared Facilities" shall have the meaning set forth in the
           -------------------------
     Recitals hereto.

          "Consulting Engineer" shall mean an independent firm of professional
           -------------------
     engineers providing professional services in the fields of engineering,
     design and construction management of electric generating facilities,
     reasonably chosen by the Company and reasonably acceptable to the Owner
     Lessor, provided, that at any particular time there shall be no more than
     one Consulting Engineer.

          "Contract Year" shall mean the 12-month period commencing at 12:01
           -------------
     a.m. on January 1 of each year and ending at 12:00 a.m. on the following
     January 1, except that the first Contract Year shall begin on the Lessor
     Possession Date and shall end at 12:00 a.m. on the following January 1.

          "Contractor" shall have the meaning set forth in Section 3.3 hereof.
           ----------

          "Event of Force Majeure" means any event which is not within the
           ----------------------
     reasonable control of the Company or the Owner Lessor and which directly or
     indirectly makes continued operation of the Company Owned Facilities or the
     Owner Lessor Owned Facilities impracticable including, the following, to
     the extent they meet the foregoing conditions: any type of labor dispute or
     industrial action of any kind (including, a strike, interruption, slowdown
     and other similar action on the part of organized labor), any lockout, act
     of public enemy, war (declared or undeclared), civil war, sabotage,
     blockade, revolution, riot, insurrection, civil disturbance, terrorism,
     epidemic, cyclone, tidal wave, landslide, lightning, earthquake, flood,
     storm, fire, adverse weather conditions, explosion, breakage or accident to
     machinery or equipment or pipe or transmission line or other facility,
     embargo, and any inability to obtain or delay in obtaining permits,
     approvals, equipment, materials or transport.

                                       2
<PAGE>

          "Expiration Date" shall mean the last day of the term of this
           ---------------
     Agreement in accordance with Section 2.1 of this Agreement.

          "Owner Lessor Owned Facilities" shall mean the Facility, consisting of
           -----------------------------
     electric generating and  related facilities located on the Facility Site or
     on adjacent properties and sold to the Owner Lessor pursuant to the Deed
     and the Bill of Sale, including but not limited to the Owner Lessor Shared
     Facilities.  The Owner Lessor Owned Facilities do not include the Retained
     Assets.

          "Owner Lessor Shared Facilities" shall have the meaning set forth in
           ------------------------------
     the Recitals hereto.

          "Parts" shall mean all appliances, parts, instruments, appurtenances,
           -----
     accessories, furnishings and other equipment of whatever nature that may
     from time to time be incorporated or installed in or attached to the Shared
     Facilities.

          "Permitted User" shall mean the Owner Lessor, the Company, an
           --------------
     Additional Owner, any such Party's Affiliates or any such Party's
     Contractor.

          "Permitted Transferee" shall mean any Person that (1) at the time of
           --------------------
     the relevant transfer referred to in Section 5.4, is not the subject of any
     bankruptcy, insolvency or similar proceeding, and (2) unless waived by the
     other Party at the time of such transfer, has (or its beneficial owner or
     the guarantor of either of the foregoing has) a net worth of at least
     Seventy-Five Million and 00/100 Dollars ($75,000,000).

          "Shared Facilities" shall have the meaning set forth in the Recitals
           -----------------
     hereto.

     SECTION 1.2 Use of Definitions.  All terms defined in this Agreement shall
have the defined meanings when used in any certificate, report or other document
made or delivered pursuant to this Agreement.

                                  ARTICLE II

                             EFFECTIVE DATE; TERM

     SECTION 2.1 Effective Date of Agreement. This Agreement shall be effective
on and as of the date hereof (the "Effective Date"); provided, however, that no
                                   --------------
Party shall have any obligation under Article 3 or 4 hereof until the Lessor
Possession Date with respect to any Unit; provided, further, however, that this
Agreement shall not in any way affect the respective rights and obligations of
the Parties under the terms of any of the Operative Documents which may then
still be in effect. Nothing herein contained shall be construed as requiring the
other Party to take, or cause the taking of, any action in violation of or to
prevent the other Party from exercising, or causing the exercise of, any of such
Party's rights under, the Facility Lease. Prior to the Lessor Possession Date
with respect to any Unit, the duties, responsibilities and rights of the Company
in respect of the Facility shall be governed exclusively by the terms of the
Facility Lease.

                                       3
<PAGE>

     SECTION 2.2 Term.  The term of this Agreement shall commence on the
Effective Date and shall expire on the earliest of (a) the last day of the Site
Lease Term, (b) any earlier termination in accordance with Section 4.3, or (c)
at such other time as may mutually be agreed upon by each of the Parties hereto;
provided, however, that, in no event shall such term expire prior to release of
the Lien of the Lease Indenture Trustee under the Lease Indenture without the
consent of the Lease Indenture Trustee.  Upon the expiration of the term of this
Agreement, all rights with respect to the Shared Facilities granted and conveyed
herein shall terminate.

                                  ARTICLE III

                               SHARED FACILITIES

     SECTION 3.1 Use of Shared Facilities.  The Company and the Owner Lessor
each hereby agrees to operate (or cause the operation in accordance with Section
3.2 hereof) the Company Shared Facilities and the Owner Lessor Shared
Facilities, respectively, for its own benefit and for the benefit of the other
Party (and, in the case of the Owner Lessor, for the benefit of any Additional
Owner) to the extent necessary or useful in connection with the use and
enjoyment of the Company Owned Facilities or the Owner Lessor Owned Facilities,
as the case may be, during the term of this Agreement.

     SECTION 3.2 Ownership of Shared Facilities.  Notwithstanding the provisions
of any other agreement between the Company and the Owner Lessor, the Company
shall at all times own the Company Owned Facilities, and the Owner Lessor shall
at all times own the Owner Lessor Owned Facilities.

     SECTION 3.3 Operation and Maintenance of Shared Facilities.  At all times
during the term of this Agreement, each Party shall, or shall cause a Person
which is at all times qualified and licensed or otherwise authorized under any
Applicable Law to operate the Shared Facilities (including, in respect of the
Owner Lessor, the Company) (such Person, such Party's "Contractor") to, use,
                                                       ----------
operate, maintain, inspect, service, repair, rebuild and overhaul the Shared
Facilities owned by such Party, and each Part thereof, or cause the same to be
operated, maintained, inspected, serviced, repaired, and overhauled in good
operating order, repair and condition, reasonable wear and tear excepted,
consistent with Prudent Industry Practice and in accordance with any Applicable
Law and in such a manner as not intentionally to cause a material decrease or
diminution of the value, residual value, utility or remaining useful life of any
of the Owner Lessor Owned Facilities or Company Owned Facilities, as the case
may be, reasonable wear and tear excepted; provided, however, that, such Party
shall not be obligated to comply with any Applicable Law in respect of the
matters hereinabove referred to, so long as such failure of compliance shall not
involve:

          (a)  a material risk of the foreclosure, sale, forfeiture or loss of
     any of the Owner Lessor Owned Facilities, the Company Owned Facilities, the
     Facility Site and the Retained Sites, or any material part of any of the
     foregoing;

          (b)  a material adverse effect on the use, operation or maintenance of
     the Company Owned Facilities or the Owner Lessor Owned Facilities;

                                       4
<PAGE>

          (c)  a material decrease or diminution of the value, utility or
     remaining useful life of any of the Company Owned Facilities or the Owner
     Lessor Owned Facilities; or

          (d)  a risk of (or, except with respect to the risk of criminal
     liability, if the application or validity of such Applicable Law is being
     contested diligently and in good faith by appropriate proceedings, a
     material risk of) criminal liability or civil liability being incurred by
     any Transaction Party (other than such Party or such Party's Contractor)
     and, solely in the case of such civil liability, either (i) such Party has
     not agreed, in a written instrument in form and substance reasonably
     satisfactory to such Transaction Party, to indemnify such Transaction Party
     against the payment thereof or (ii) the event or events in question are
     recurring and are of such a nature so as to subject the other Party or any
     of its Affiliates to material adverse publicity or other consequences for
     which compensation in the form of reimbursement of monetary damages is, in
     the good faith judgment of such Person, not sufficient, and such Party
     fails to pursue diligently the cure of such event.

     SECTION 3.4 Insurance for Shared Facilities.

          (a)  General Coverage.  At all times during the term of this
               ----------------
     Agreement, each Party will cause to be carried and maintained on or with
     respect to the Company Shared Facilities or Owner Lessor Shared Facilities,
     as the case may be, with insurers of recognized responsibility selected by
     such Party, (i) insurance against damage to or destruction of such Shared
     Facilities and (ii) liability insurance with respect to third Party
     personal injury and property damage, in each case in such amounts and
     against such risks as is customary with companies with the same or similar
     facilities using Prudent Industry Practice.

          (b)  Application of Proceeds.  All proceeds of any insurance against
               -----------------------
     damage to or destruction of the Shared Facilities relating to an Event of
     Loss involving such Shared Facilities shall be paid to the Party owning
     such Shared Facilities, and such Party shall apply such proceeds first, in
     payment for the repair or restoration of such Shared Facilities, to the
     extent necessary so that the condition of such Shared Facilities after such
     repair or replacement shall be at least equivalent to the condition thereof
     before the occurrence of such Event of Loss (on the assumption that such
     Shared Facilities were, immediately prior to the occurrence of such Event
     of Loss, being maintained in accordance with the terms of this Agreement),
     if such repair or restoration has not already been paid for by such Party;
     provided, however, that such application of such proceeds shall be required
     only to the extent that services affected by such Event of Loss are not
     available from third parties at rates comparable to the rates payable to
     such Party for such services hereunder; and second, to reimburse such Party
     for any such payment or service made by such Party in connection with such
     repair or restoration, and any balance remaining shall be retained by or
     paid to such Party for its own account.

     SECTION 3.5 Non-Exclusive Right to Use, Control of Shared Facilities.
Notwithstanding anything herein contained to the contrary, it is expressly
understood and agreed that the Shared Facilities shall be made available for the
use and benefit of the Owner Lessor Owned Facilities and the Company Owned
Facilities on a nondiscriminatory basis, and all rights

                                       5
<PAGE>

of the other Party hereunder shall be subject to all reasonable operational,
environmental and safety rules and procedures required by the applicable
Permitted User. Notwithstanding any provision herein to the contrary, if the
Shared Facilities are, at any time, insufficient to allow the Owner Lessor Owned
Facilities and the Company Owned Facilities, as the case may be, to operate in
substantially the same manner and to substantially the same extent as was
permitted prior to the Effective Date because of the construction of an
Additional Facility, the Owner Lessor shall have priority use of the Shared
Facilities in such amounts and for such time as required to allow the Owner
Lessor Owned Facilities to operate, as to any Unit, in substantially the same
manner and to substantially the same extent as such Unit was operated
immediately prior to the Effective Date or immediately prior to the Lessor
Possession Date as to such Unit, whichever such period used for measuring
operating levels results in higher priority use for the Owner Lessor Owned
Facilities. Prior to a Lessor Possession Date, the parties agree to cooperate
with each other and to enter into mutually agreeable arrangements, each acting
reasonably and in good faith, with respect to joint operation, maintenance and
use of, and allocations of costs and expenses with respect to the Shared
Facilities; provided, that all costs and expenses shall be shared by the parties
based upon their respective utilization of the Shared Facilities.

     SECTION 3.6 Force Majeure.  No Party hereto shall be considered to be in
default in the performance of any of the obligations hereunder, other than
obligations of the Parties hereto to pay amounts due hereunder, if failure of
performance shall be due to an Event of Force Majeure.  Any Party hereto
rendered unable to fulfill any obligation by reason of an Event of Force Majeure
shall give prompt notice of the same to the other Party, detailing such Event of
Force Majeure and thereafter exercise due diligence to remove such inability
with all reasonable dispatch. Payment obligations of either Party hereunder may
be suspended to the extent and for so long as either Party's performance
hereunder is suspended due to an Event of Force Majeure, except with regard to
payment for services actually rendered and for such Shared Facilities made
available prior to or during the occurrence of such Event of Force Majeure.

     SECTION 3.7 Condemnation of Shared Facilities.  In the event all or any
part of the Company Shared Facilities or Owner Lessor Shared Facilities, as the
case may be, shall be taken by appropriation for public or quasi-public use
under the right of eminent domain or otherwise, the award made by the condemning
authority shall be distributed to the Company or the Owner Lessor, as their
interests may appear.  The Company or the Owner Lessor, as the case may be,
shall apply all proceeds of the condemnation award received by it in respect of
the Company Shared Facilities or the Owner Lessor Shared Facilities, as the case
may be, toward the costs of repairing or replacing such Shared Facilities or the
part thereof which has been damaged; and any such proceeds not required for such
purpose shall be distributed to the other Party to the extent of the value of
its interest in such Shared Facilities granted and conveyed hereunder.

     SECTION 3.8 Survival of Rights in Shared Facilities.  Except as provided in
Section 2.2, this Agreement shall not terminate, nor shall any of the rights in
the Shared Facilities granted and conveyed hereunder be extinguished, lost,
conveyed or otherwise impaired, in whole or in part, by any cause or for any
reason whatsoever, including, the following: (a) the occurrence or existence of
any Lease Event of Default; (b) any damage to or destruction of all or any part
of the Company Owned Facilities or the Owner Lessor Owned Facilities, or the
taking of the Company Owned Facilities or the Owner Lessor Owned Facilities or
any portion thereof by expropriation, condemnation or otherwise; (c) any
prohibition,

                                       6
<PAGE>

limitation or restriction of any Party's use of all or any part of its property
or the interference of such use by any Person, or any eviction by any person
holding superior title or otherwise; (d) the termination or loss of the interest
of the Owner Lessor or the Company under the Facility Lease; (e) the assumption
by the Company of the obligations of the Owner Lessor under the Certificates,
the Lease Indenture or any other Operative Document; (f) the coincident
ownership by any Person of any estate or interest in any of the Shared
Facilities and other rights granted and conveyed pursuant to this Agreement with
any estate or interest in the Facility Site and the Retained Sites or any part
thereof; (g) any inadequacy, incorrectness or failure of the description of the
Facility Site, the Retained Sites, the Shared Facilities or any property or
rights intended to be granted or conveyed by this Agreement; (h) any default in
the performance or the observance by any Party hereto of any of their respective
covenants and agreements to be performed and observed by it under any of the
Operative Documents; (i) the insolvency, bankruptcy, reorganization or similar
proceedings by or against any Party hereto; (j) any non-use or excessive use of
the Shared Facilities, or (k) any other reason whatsoever, whether similar or
dissimilar to any of the foregoing.

                                  ARTICLE IV

                                    PAYMENT

     SECTION 4.1 Payment.  In consideration of the agreement of each Party to
operate its Shared Facilities and the other services to be provided by such
Party hereunder, the other Party shall pay to such Party on the January 2 or
July 2 which first succeeds the initial Lessor Possession Date, and on each
January 2 and July 2 thereafter to and including the Expiration Date (and on the
Expiration Date, if such date is not a January 2 or July 2), an amount to be
mutually agreed from time to time between the Parties, or, if at any time the
Parties cannot reach such mutual agreement, an amount equal to the Shared
Facilities Fair Market Rental Value (each a "Shared Facilities Payment").  As
                                             -------------------------
used herein, the term "Shared Facilities Fair Market Rental Value" shall mean,
                       ------------------------------------------
for any period, the amount which would be determined in an arms-length
negotiation between an informed and willing owner of property equivalent to the
Company Shared Facilities or the Owner Lessor Shared Facilities, as applicable
(under no compulsion to grant a right of use in such property) and an informed
and willing prospective user of such property (under no compulsion to use such
property) for the non-exclusive use of such property on the terms set out herein
for such period, as established as promptly as practicable after the Lessor
Possession Date, but in no event more than ninety (90) days after such date, by
the Consulting Engineer. The determination by the Consulting Engineer of the
Shared Facilities Fair Market Rental Values will be binding on each of the
Company and the Owner Lessor.  Any Shared Facilities Payments hereunder shall be
in U.S. Dollars, and shall be made to such Person and at such location as the
receiving Party shall designate in writing to the other Party from time to time.

     SECTION 4.2 Late Payments.  In the event any payment required to be made
hereunder is not submitted within the time period herein specified, the Party
failing to make such payment shall pay, in addition to the amount of the
required payment, interest at a rate per annum equal to the Overdue Rate, from
the date when such payment was due to the date of payment.

                                       7
<PAGE>

     SECTION 4.3 Payment Default.  The failure of either Party to make any
payment required to be made under Section 4.1 within 30 days after receipt of
written notice of such nonpayment shall constitute a default hereunder. If any
such default occurs and is continuing, the non-defaulting Party may, in its sole
discretion, either (i) terminate this Agreement by giving written notice to the
defaulting Party, which termination shall be effective on a date specified in
such notice that is no earlier than 30 days following the date of such notice
unless such default shall have been cured prior to such specified date; or (ii)
suspend performance of its obligations hereunder (but shall be entitled to
receive services from the defaulting party hereunder); provided that if the Lien
of the Lease Indenture shall not have been discharged, or if any lease or
mortgage financing has been obtained with respect to any Additional Facility and
has not been discharged, the non-defaulting Party shall notify the Lease
Indenture Trustee or such other financing parties, as the case may be, of such
default and the intention to terminate, and such termination shall be subject to
any cure rights granted to the Lease Indenture Trustee under the Lease Indenture
or to such other financing parties under the applicable financing documents.

     SECTION 4.4 Right of Setoff.  On each Payment Date, all amounts required to
be paid by either Party hereunder may be set off against any amount required to
be paid to the other Party pursuant to Section 4.1 of this Agreement. The owing
Party shall pay any balance due to the other Party on each such Payment Date.

                                   ARTICLE V

                                 MISCELLANEOUS

     SECTION 5.1 Amendments and Waivers.  No term, covenant, agreement or
condition of this 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 5.2 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:

                                       8
<PAGE>

     If to the Company:

          Dynegy Roseton, L.L.C.
          c/o Dynegy Northeast Generation, Inc.
          992 River Road
          Newburgh, New York 12550
          Telephone No.: (845) 563-4961
          Facsimile No.: (845) 563-4992
          Attention: Daniel P. Thompson, Vice President, Operations

          with a copy to:

          Dynegy Power Corp.
          1000 Louisiana Street, Suite 5800
          Houston, Texas 77002
          Telephone No.: (713) 507-6823
          Facsimile No.: (713) 767-8510
          Attention: Timothy A. Beverick, Esq.

     If to the Owner Lessor:

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

          with a copy to the Lease Indenture Trustee and the Pass Through
          Trustees:

          The Chase Manhattan Bank
          Institutional Trust Services
          450 West 33rd Street, 15th Floor
          New York, New York 10001
          Telephone No.: (212) 946-7557
          Facsimile No.: (212) 946-8177/8178
          Attention: Annette M. Marsula, Vice President
                     International/Project Finance Team

     SECTION 5.3 Successors and Assigns.  This 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 permitted assigns as permitted by and
in accordance with the terms hereof.

     SECTION 5.4 Transfers and Assignments.  The Owner Lessor may not assign or
otherwise transfer its rights or obligations under this Agreement to any Person
except as part of the Owner Lessor's transfer of the Owner Lessor's Interest
pursuant to the Operative Documents.

                                       9
<PAGE>

The Company may not assign or otherwise transfer its rights or obligations under
this Agreement to any Person, except that the Company may transfer or assign its
rights and obligations hereunder in whole or in part to an Additional Owner or
to a Lessee Transferee in accordance with Section 13.2 of the Participation
Agreement. Neither the Company nor the Owner Lessor shall (nor shall it permit
any other Person within its control to), without the prior written consent of
the Company or the Owner Lessor, as the case may be, which consent shall not be
unreasonably withheld, sell, assign, lease or otherwise transfer the Company
Shared Facilities or the Owner Lessor Shared Facilities, as the case may be, to
any Person that is not a Permitted Transferee, except for sales of assets no
longer used or useful hereunder. The Company or the Owner Lessor, as applicable,
shall cause each Person to whom the Company or the Owner Lessor shall sell,
assign, lease or otherwise transfer the Company Shared Facilities or the Owner
Lessor Shared Facilities, as the case may be, (other than in connection with any
sale of assets no longer used or useful hereunder) to enter into an agreement
assuming the obligations of the Company or the Owner Lessor hereunder, as
applicable, in form and substance satisfactory to the Company or the Owner
Lessor, as the case may be (accompanied by such opinions of counsel,
certificates and other documents as the Company and the Owner Lessor shall
reasonably request). Upon the execution and delivery of such new agreement by
the transferee, assignee or tenant to the Company or the Owner Lessor, this
Agreement shall terminate with respect to the Company or the Owner Lessor, as
the case may be, and such party shall be fully released from all obligations and
liabilities hereunder; provided, that in the case of a partial assignment or
transfer to an Additional Owner, such termination and such release shall be
applicable only to the rights and obligations assigned or transferred.

     SECTION 5.5  Governing Law. This Agreement 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 provision thereof, other than New York General
Obligations Law Section 5-1401).

     SECTION 5.6  Severability. Any provision of this 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 5.7  Counterparts. This Agreement may be executed 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 5.8  Headings and Table of Contents.  The headings of the sections
and the table of contents of this Agreement 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 5.9  Further Assurances.  Each party hereto will promptly and duly
execute and deliver such further documents and to make such further 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 Agreement.

                                      10
<PAGE>

     SECTION 5.10  Limitation of Liability. It is expressly understood and
agreed by the parties hereto that (a) this Agreement is executed and delivered
by Wilmington Trust Company ("Wilmington"), not individually or personally but
                              ----------
solely as Lessor Manager under the LLC Agreement, in the exercise of the powers
and authority conferred and vested in it pursuant thereto, (b) each of the
representations, undertakings and agreements herein made on the part of the
Owner Lessor is made and intended not as personal representations, undertakings
and agreements by Wilmington but is made and intended for the purpose for
binding only the 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 the Owner Lessor or be liable for the breach or failure of any obligation,
representation, warranty or covenant made or undertaken by the Owner Lessor
under this Agreement.

                                      11
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement as
of the day and year first written above.

                              DYNEGY ROSETON, L.L.C., a Delaware limited
                              liability company

                              By: _______________________________
                                  Name:
                                  Title:

                              ROSETON OL LLC

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

                                  By:____________________________
                                     Name:
                                     Title:
<PAGE>

                                                                       EXHIBIT A

                           Company Shared Facilities
                           -------------------------


Miscellaneous
-------------
 .  Administration Building
 .  Site Security Buildings
 .  Warehouses, Receiving, Storage and Inventory Control Facilities
 .  Storerooms
 .  Security Fencing and Entry Gates
 .  Maintenance Management System Data Base

                                   EXH. A-1
<PAGE>

                                                                       EXHIBIT B

                         Owner Lessor Shared Facilities
                         ------------------------------

Generating Station/General
--------------------------
 .  Wastewater Treatment Facility
 .  Waste Treatment Ponds
 .  Cooling Water Intake and Discharge System
 .  City Water Supply Mains and Metering Devices
 .  R-S Tie Line for Start-up and Auxiliary Power
 .  Auxiliary Boiler
 .  Switchgear, Load Centers and Motor Control Centers for Units 1 and 2
 .  Makeup Water Demineralizer

Buildings
---------
 .  Main Building Housing Units 1 and 2, including
 .  Administrative Offices in the Main Building
 .  Chemistry Laboratory
 .  Maintenance Shops
 .  Control Room
 .  Building Heating and Ventilation System
 .  Training Rooms
 .  Locker Rooms, Showers, Toilets, Lunch Rooms, Kitchen
 .  Elevators

Environmental
-------------
 .  Sewage Collection and Treatment Facility
 .  Chemical Spill Control, Containment Equipment and Storage Tanks
 .  Oil/Water Separators
 .  Solid Waste Collection and Disposal Equipment
 .  Water Treatment for Effluent
 .  Bottom Ash/Salt Storage Building
 .  Oil Spill Containment Boom

Fire Protection/Prevention System
---------------------------------
 .  Hydrant and Hose Stations
 .  Fire Detection System
 .  Pump Houses
 .  Co2 and Chemical Systems

Fuel Supply
-----------
 .  Fuel Oil Storage Tank Farm - Six 8,000,000 gallon No. 6 Fuel Oil Tanks
 .  One 150,000 gallon No. 2 Fuel Oil Tank
 .  Fuel Oil Transfer Pump Houses

                                 EXH. B-1
<PAGE>

 .  Oil Pipelines between Facility/Storage Tanks and the Fuel Oil Pump House
 .  Fuel Oil and Natural Gas Metering Devices
 .  Natural Gas Supply Main from Regulator Station to Facility - all piping and
   equipment from the discharge of the shut-off valves to Facility, including
   the relief valve
 .  Gas Chromatograph
 .  Dock equipment and facilities that are not included in the definition of
   Dock Facilities (as defined in Appendix A to the Participation Agreement)
 .  Fuel Oil Heat Tracing System

Communication
-------------
 .  Plant Monitoring System
 .  Any copper communication cables and associated terminating equipment
   located on site that is not owned by Central Hudson
 .  Equipment installed at the plant for purposes of radio communications
   (excluding portable communications equipment)
 .  All fiber optic cables, including the cable that connects the Danskammer
   and Roseton Plants, and the associated terminating equipment.  This equipment
   includes fiber optic cables, fiber optic terminal equipment, and associated
   multiplexing equipment, racks, and patch panels
 .  Telephone Vault
 .  Plant PA/Paging System

Transmission and Start-up Transformers
--------------------------------------
 .  High -Voltage Electrical Equipment (as defined in Appendix A to the
   Participation Agreement)
 .  2 Start-up Transformers (located in Danskammer substation)
 .  2 Station Service/Start-Up Power Breakers and Associated Switches (located
   in Danskammer substation)

Miscellaneous
-------------
 .  Perimeter Lighting
 .  Bulk Chemical Storage System (Hydrogen, CO2 Nitrogen, Lubricants)
 .  Cathodic Protection Systems
 .  Area Lighting (Powerhouse, Dock, Fuel Terminal, Parking Areas)

                                   EXH. B-2