N.Y. Rapid Transit Law § 43

§ 43. Persons with whom contracts may be made. Nothing contained in\nthis chapter shall be deemed, or be construed as intending to limit, or\nas limiting, in any manner, the discretion of the board of\ntransportation, provided in the opinion of the board of estimate and the\nmayor, it is expedient, practicable and in the public interest to do so,\nto enter into contracts for construction, equipment, maintenance and\noperation with the same person, or for any one or more of such purposes\nwith the same person or with different persons either in one contract or\nin separate contracts, and at any time or times.\n