§ 127. Franchises and privileges. Without first having obtained the permission and approval of the commissioner no common carrier shall begin the construction of a railroad or street railroad, or any extension thereof, for which a certificate of public convenience and necessity shall not have been granted by the board of railroad commissioners or where prior to said time said common carrier shall not have become entitled by virtue of its compliance with the provisions of the railroad law to begin such construction; nor, except as above provided in this section, shall any such common carrier exercise any franchise or right under any provision of the railroad law, or of any other law, not heretofore lawfully exercised, without first having obtained the permission and approval of the commissioner. The commissioner shall have power to grant the permission and approval herein specified whenever he shall after due hearing determine that such construction or such exercise of the franchise or privilege is necessary or convenient for the public service.