Section 47. The department may, after notice and a public hearing, authorize a town which has acquired a municipal lighting plant to extend its mains or lines into an adjoining town in order to distribute and sell gas or electricity therein, if such town or a private corporation therein is not then supplying such town with gas or electricity, as the case may be. Such authorization shall be upon such terms and with such limitations and restrictions as the department deems for the public interest. A town so authorized shall thereafter have in such adjoining town the same rights and privileges, and be subject to the same limitations and obligations, as it has within its own territorial limits.