Other utilities. Prior to the granting of final approval, the developer shall have arranged with all serving utilities, including, without limitation, electric, gas and telephone utilities, for the underground installation of the utilities' distribution supply lines, and service connections in accordance with the provisions of the applicable standard terms and conditions incorporated as a part of its tariff, as the same are then on file with the State of New York Board of Public Utility Commissioners, and shall submit to the approving agency prior to the granting of final approval a written instrument from each serving utility which shall evidence full compliance with the provisions of this subsection; provided, however, that the approving agency, in its sole discretion, may permit developments on lots which abut existing streets where overhead utility distribution supply lines have theretofore been installed on any part thereof to be supplied with electric and telephone service from such overhead lines or extension thereof, but in such event the service connection from such overhead lines shall be installed underground.