53 Pa. Stat. § 25493
Cities of the second class may construct, and operate and maintain, underground tubes, or tunnels or subways, under public highways and public property and private property. Such tubes, tunnels, or subways may be used for such lawful purposes as shall be designated, from time to time, by ordinance.
The city may provide for entrances and exits to and from any such tunnel, tube, or subway; and may grant rights of entrances to any part of such tube, tunnel, or subway to individuals, copartnerships, corporations, or associations. Entrances and exits may be on a public highway, public property, and on private property.
The city may construct and maintain the necessary openings, entrances, vaults, and manholes; and may construct, install, and maintain tracks, platforms, stations, equipment, and appliances therein and connected therewith, as may be useful and necessary for the full and complete use thereof by the general public, the said city, and the said persons, firms, and corporations using or intending to use the same.
53 P.S. § 25493