(a) On timely filing of a petition for intervention, any municipality shall be allowed to intervene, on behalf of persons located within the boundary line of such municipality, in any rate proceeding before the state corporation commission that involves the rates of a public utility serving persons located within the boundary line of such municipality.
(b) For the purposes of this section, "municipality" means any county, township, city, school district or other political or taxing subdivision of the state.