Cal. Pub. Util. Code § 1702

Complaint may be made by the commission of its own motion or by any corporation or person, chamber of commerce, board of trade, labor organization, or any civic, commercial, mercantile, traffic, agricultural, or manufacturing association or organization, or any body politic or municipal corporation, by written petition or complaint, setting forth any act or thing done or omitted to be done by any public utility, including any rule or charge heretofore established or fixed by or for any public utility, in violation or claimed to be in violation, of any provision of law or of any order or rule of the commission. No complaint shall be entertained by the commission, except upon its own motion, as to the reasonableness of any rates or charges of any gas, electrical, water, or telephone corporation, unless it is signed by the mayor or the president or chairman of the board of trustees or a majority of the council, commission, or other legislative body of the city or city and county within which the alleged violation occurred, or by not less than 25 actual or prospective consumers or purchasers of such gas, electricity, water, or telephone service.