Section 43. Persons with whom contracts may be made

Nothing contained in
  this chapter shall be deemed, or be construed as intending to limit,  or
  as   limiting,   in   any   manner,  the  discretion  of  the  board  of
  transportation, provided in the opinion of the board of estimate and the
  mayor, it is expedient, practicable and in the public interest to do so,
  to enter into contracts for  construction,  equipment,  maintenance  and
  operation  with the same person, or for any one or more of such purposes
  with the same person or with different persons either in one contract or
  in separate contracts, and at any time or times.