Section 21. A company incorporated for the transmission of intelligence by electricity or by telephone, whether by electricity or otherwise, or for the transmission of television signals, whether by electricity or otherwise, or for the transmission of electricity for lighting, heating or power, or for the construction and operation of a street railway or an electric railroad, may, under this chapter, construct lines for such transmission upon, along, under and across the public ways and, subject to chapter ninety-one, across and under any waters in the commonwealth, by the erection or construction of the poles, piers, abutments, conduits and other fixtures, except bridges, which may be necessary to sustain or protect the wires of its lines; but such company shall not incommode the public use of public ways or endanger or interrupt navigation. This section shall apply to a company incorporated under the laws of another state for the transmission of intelligence by electricity or by telephone, or television, whether by electricity or otherwise, and which is engaged in interstate commerce within the commonwealth. This section shall apply to a municipal lighting plant or cooperative that operates a telecommunications system outside the limits of its service territory pursuant to section 47E of chapter 164, but only for construction that is outside its service territory.