Section 22G. The board of selectmen or city council of any municipality may grant special permission, for such period and on such terms as it may deem appropriate, in cases of emergency or unusual circumstances, without discrimination as to any person or utility, to erect, construct, install, maintain, use or operate, poles and overhead wires and associated overhead structures, notwithstanding the provisions of any ordinance or by-law adopted pursuant to section twenty-two C or twenty-two D. No person shall be deemed to have violated any ordinance or by-law adopted pursuant to section twenty-two C or section twenty-two D for doing any act authorized by any such special permission.