(1) This part shall not be construed as repealing or impairing any provision of any special or private act relating to the regulation of buildings in mapped highways, and all the provisions of the private act shall remain in full force and effect; but insofar as this part is not inconsistent with the special or private act, this part shall apply to the powers and authorities of the county or municipality.
(2) This part shall apply to counties and cities within counties having a population of not less than three hundred seventy-five thousand (375,000), according to the 1960 federal census or any subsequent federal census.
(3) This part shall apply to counties with a population in excess of two hundred thousand (200,000).