SECTION 1. Section 2ZZZ of chapter 29, as appearing in the 2018 Official Edition, is hereby amended by inserting after subsection (d) the following subsection: (e) In addition to the revenues credited to the Massachusetts Bay Transportation Authority in subsections (c) and (d) of this section and to the regional transit authorities in subsection (d) of this section, the state treasurer acting on behalf of the commonwealth shall enter into an agreement with the Massachusetts Bay Transportation Authority providing that the commonwealth shall provide contract assistance from the Commonwealth Transportation Fund, from funds not otherwise required to be paid to the Massachusetts Bay Transportation Authority, or the regional transit authorities, including but not limited to any additional contract assistance in existence during Fiscal Year 2016 or at the time of passage of this law for all debt service obligations of the Massachusetts Bay Transportation Authority originally derived from the Central Artery obligations of the commonwealth. Such contract assistance agreement shall provide for the payment by the commonwealth of such debt service obligations of the Massachusetts Bay Transportation Authority at such time during each such fiscal year and upon such terms and under such conditions as the Massachusetts Bay Transportation Authority may stipulate. The Massachusetts Bay Transportation Authority may pledge such agreement and the rights of the Massachusetts Bay Transportation Authority to receive amounts thereunder as security for the payment of debt obligations issued by the Massachusetts Bay Transportation Authority. Such agreement shall constitute a general obligation of the commonwealth for which the faith and credit of the commonwealth shall be pledged for the benefit of the Massachusetts Bay Transportation Authority and of the holders of any debt obligations of the Massachusetts Bay Transportation Authority which may be secured by a pledge of such agreement or of amounts to be received by the Massachusetts Bay Transportation Authority under such agreement. The secretary of administration and finance shall calculate annually the portion of the Massachusetts Bay Transportation Authority debt that originates from the Central Artery obligations of the commonwealth.