Whenever any franchises as are required by sections 24 and/or 25 of article 8 of the constitution of the state of Michigan have heretofore been approved by the requisite majority of the qualified voters of any city having a population not to exceed 15,000 according to the last federal census, as fixed by the several enabling acts under which the election was held, the said franchises as so approved by the voters are hereby confirmed and validated and declared to be legal and binding franchises of the city if, as and when so approved by the voters, notwithstanding said franchises fail to fix rates and/or charges to be made by the grantee in said franchises, and notwithstanding said franchises delegate to the city council and/or the grantee in said franchises the power to agree upon rates and/or charges, and notwithstanding said franchises provide that if rates and/or charges cannot be agreed upon between said city and the grantee in said franchise, said rates and/or charges may be fixed by the Michigan public utilities commission, or its successors, from time to time upon the application of either party to said franchise after due hearing thereon, and notwithstanding said franchises may be invalid as to any matter of substance or form.