Cal. Public Utilities Code § 465

(a) Except as provided in subdivision (c), whenever any labor of a custodial or janitorial nature is not performed by the employees of a public utility, such labor shall be let out under contract to the lowest responsible bidder with the provision that prevailing wages be a condition of any such contract. For the purposes of this section, “prevailing wages” shall be deemed to include employer payments for health and welfare, pension, holidays, sick leave, vacation, apprenticeship or other training programs. (b) A public utility shall implement the provisions of subdivision (a) by requiring the entity with which it contracts to pay its custodial or janitorial employees the prevailing wage. The public utility awarding the contract shall cause to be inserted in the contract a stipulation that the failure to pay prevailing wages shall be cause for the termination of the contract. (c) Nothing in this section shall prevent a public utility from employing a custodial or janitorial service for a period of 90 days or less without a contract meeting the requirements of subdivision (a) of this section. (d) The Director of the Department of Industrial Relations shall determine the prevailing wage for custodial or janitorial employees in accordance with the standards set forth in Section 1773 of the Labor Code.