California Code, Insurance Code - INS § 11586

(a) On and after the effective date of this section, each insurer licensed to issue automobile liability insurance or common carrier liability insurance, and selling or offering for sale automobile liability insurance or common carrier liability insurance to a transit district organized under Part 3 (commencing with Section 30000) of Division 10 of the Public Utilities Code, shall, as a condition of obtaining or retaining a license to transact business in this state, offer uninsured motorist coverage identical in all respects to that set forth in Section 11580.2 with regard to private passenger motor vehicles, except that the insurer and such transit district, as the case may be, may not agree to waive such coverage.

(b) No insurer subject to subdivision (a) shall refuse to issue uninsured motorist coverage to any such transit district which applies to it therefor.

(c) Each insurer subject to this section may charge such premium rate for providing uninsured motorist coverage to such transit district as will be sufficient for it to meet the costs of providing such coverage.