§ 26. Extension of lines. A telegraph corporation, a telephone corporation or a telegraph and telephone corporation heretofore or hereafter incorporated under or by any general or special law may construct, own, use and maintain any line of electric telegraph or telephone, whether or not the line and the territory in which it be located was described in its original certificate of incorporation, and whether wholly within or wholly or partly without the state, and may join with any other corporation in constructing, leasing, owning, using and maintaining such line, or hold or own any interest therein, or become lessees thereof, upon delivering to the department of state for filing a certificate of amendment. If the lines or territory are to be extended the certificate shall describe the territory in which the operations of the corporation are to be carried on.