This chapter shall not apply to any existing or proposed building
or extension thereof used or to be used by public service corporations,
if, upon petition of the corporation, the Public Utility Commission
shall, after a public hearing, decide that the present or proposed
situation of the building in question is reasonably necessary for
the convenience or welfare of the public.
Should any section or provision of this chapter be declared
by the courts to be invalid, the same shall not affect the validity
of the chapter as a whole or any part thereof other than the part
so declared to be invalid.