Section 18. To the extent that funds paid to the authority pursuant to section 35T of chapter 10 are insufficient in any year to meet the debt service or other payment obligations of the authority in connection with debt or other financing obligations of the authority, including, without limitation, leases, reimbursement obligations or interest exchange agreements, issued or entered into prior to July 1, 2000 in respect of which the commonwealth has pledged its credit or is otherwise liable or as to which the authority has covenanted to maintain net cost of service or contract assistance support, the commonwealth shall remain liable for the payment of such obligations or the provision of net cost of service or contract assistance support as to such obligation to the same extent as before the enactment of this chapter; provided, that the amount of any such support provided by the commonwealth to the authority pursuant to this section shall be in the form of a no-interest loan repayable within five years from the dedicated revenue source and system revenues of the authority. Notwithstanding the provisions of this section, the commonwealth may, subject to appropriation and the provisions of article 62 of the Constitution of the Commonwealth, pledge its credit, guaranty, or support for the funding of transit commitments made in connection with the central artery project, so-called, capital improvements required under the Americans With Disabilities Act, or any other projects to conform to federal statutory mandates, or projects or services specifically authorized and funded by legislation enacted by the general court after July 1, 2000, or any other projects or services authorized by the general court prior to said July 1 for which funding is appropriated by the general court subsequent to said July 1; provided, that the authority shall not be obligated to make expenditures for any such commitments or projects so authorized for which the funds necessary to complete and operate such commitments or projects, including the guarantee of contract assistance, have not been made available to the authority. The authority shall undertake such projects and services so authorized and funded and shall incorporate them into the capital investment program established pursuant to paragraph (g) of section 5 and shall not make them subject to the priority ranking established by said paragraph (g) for other projects of the authority.

If at any time any principal or interest is due or about to come due on any bond or note issued or assumed by the authority prior to July 1, 2000, other than any principal or interest on any bond anticipation note guaranteed by the commonwealth, or any payment is due or about to come due under any other financing obligation undertaken or assumed by the authority prior to July 1, 2000, including without limitation a lease, a reimbursement agreement, or an interest exchange agreement, and funds to pay the same are not available, the directors shall certify to the state treasurer the amount required to meet such obligations, and the commonwealth shall thereupon pay over to the authority the amount so certified. If the commonwealth shall not make such payment within a reasonable time or shall not pay when required under any applicable contract assistance in effect prior to July 1, 2000. The authority or any holder of an unpaid bond or note issued or assumed by the authority as aforesaid, or any obligee in respect of any other such financing obligation, acting in the name and on behalf of the authority as aforesaid, shall have the right to require the commonwealth to pay the authority the amount remaining unpaid, which right shall be enforceable as a claim against the commonwealth. The authority or any such holder or obligee may file a petition in the superior court for Suffolk county to enforce such claim or intervene in any such proceeding already commenced, and the provisions of chapter 258 shall apply to such petition insofar as it relates to the enforcement of a claim against the commonwealth. Any such holder or obligee who shall have filed such a petition may apply for an order of said court requiring the authority to apply funds received by the authority on its claim against the commonwealth to the payment of the petitioner's unpaid obligation, and said court, if it finds such amount to be due to such holder or obligee, shall issue such an order.