No provision of this act shall deprive incorporated cities, including those specially chartered, from collections of fees from permits and inspections. Notwithstanding the provisions of sections 50-304, 50-306 and 50-606, Idaho Code, no cities, including those specially chartered, shall require occupational license fees from plumbing contractors and journeymen who possess a valid certificate of competency issued by the administrator of the division of occupational and professional licenses, except those cities that have qualified plumbing inspectors.