Section 152A. Notwithstanding the provisions of section one hundred and fifty-one, the commonwealth, acting by and through the secretary of administration, may enter into a contract or contracts with the trustees of a transportation area created under the provisions of sections one hundred and forty-three through one hundred and fifty-eight whereby the commonwealth agrees to reimburse the cities and towns comprising the area for fifty per cent of the financial deficit resulting from the operation of the area for any financial year. Contracts made by transportation areas with private carrier companies for which contract assistance is provided shall be within the limitations and subject to the terms of section twenty-three of chapter one hundred and sixty-one B so far as applicable and such contracts shall be eligible for contract assistance as herein provided.