Section 209. Change of motive power authorized

Any railroad company having
  the right to use any railroad now constructed in any public tunnel, road
  or  way depressed below the surface of and wholly within any public park
  in any city within the state of New York  having  a  population  of  one
  million  five  hundred  thousand or upwards, may change the motive power
  and operate any such railroad by cable  power,  underground  current  of
  electricity,  compressed  air,  or  any  other  motive  power other than
  locomotive steam power that may  be  consented  to  by  the  authorities
  having  control  of  such  park  or  parks,  and  by the commissioner of
  transportation, and may make changes in the construction of the road  or
  roadbed  or other property made necessary by the change of motive power.
  Such reconstruction shall be  at  the  sole  cost  and  expense  of  the
  railroad  company  making  such change, and when completed such improved
  railroad shall be the  property  of  the  municipal  corporation  having
  control of such public tunnel, road or depressed way.