Cal. Public Utilities Code § 240306

(a) The commission, subject to the approval of the voters, may impose a maximum tax rate of 1.5 percent under this division and the Transactions and Use Tax Law (Part 1.6 (commencing with Section 7251) of Division 2 of the Revenue and Taxation Code). The commission shall only levy a tax or multiple taxes at a rate that is a multiple of 0.25 percent, unless a different rate is specifically authorized by statute. Neither this division nor the ordinance shall affect any tax otherwise authorized. (b) Notwithstanding Section 7251.1 of the Revenue and Taxation Code, the tax rate authorized pursuant to this section shall not be considered for purposes of the combined rate limit established by that section. (c) The tax rate adopted pursuant to this chapter, unless otherwise prohibited, may be increased by the commission by ordinance adopted in the manner and by the vote stated in Section 240301 and approved by two-thirds of the electors voting on the measure at an election called for that purpose by the commission.