Section 73. A corporation subject to this chapter, to the extent that it is authorized to make, sell, transmit or distribute gas or electricity, or both, may, for the purposes of such sale, transmission, or distribution, lay, erect and maintain pipes, wires, mains and conduits under, over or across the location on private land of any railroad, electric railroad or street railway corporation at such places and in such manner and on such terms and conditions as it may agree upon with such corporation, or, in case of failure so to agree, then with the consent of the department and at such places, in such manner, with such safeguards and upon such compensation, terms and conditions as it may specify; but no pole, tower or similar structure shall be located within the location of such railroad, electric railroad or street railway corporation without its consent; provided, however, that if such corporation has lawfully constructed for such purposes poles, towers or similar structures within the location of such railroad, electric railroad or street railway corporation, then it shall not thereafter be required to remove, abandon or cease to operate such facilities without the consent of the department. If the department, after notice and public hearing, determines that the continued operation of such facilities will serve the public convenience and is consistent with the public interest, it shall specify the terms and conditions for the continued operation thereof, including compensation to any person or corporation lawfully entitled thereto. The department may, from time to time, specify such changes in the manner of laying, erecting and maintaining such pipes, mains, wires and conduits and such facilities, and, in the terms and conditions thereof, as it deems advisable.