(a) Initiative and referendum powers may be exercised by the electors of each city or county under procedures that the Legislature shall provide. Except as provided in subdivisions (b) and (c), this section does not affect a city having a charter.(b) A city or county initiative measure shall not include or exclude any part of the city or county from the application or effect of its provisions based upon approval or disapproval of the initiative measure, or based upon the casting of a specified percentage of votes in favor of the measure, by the electors of the city or county or any part thereof.(c) A city or county initiative measure shall not contain alternative or cumulative provisions wherein one or more of those provisions would become law depending upon the casting of a specified percentage of votes for or against the measure.