California Code, Public Utilities Code - PUC § 99287

(a) No provision of this article shall preclude the San Francisco Bay Area Rapid Transit District from planning, acquiring, constructing, and operating its system within or without the territory of the district as provided for by Article 5 (commencing with Section 29030), Chapter 6, Part 2 of Division 10. Notwithstanding the provisions of subdivision (d) of Section 99220, in the event an extension is to be made into a county for which services have not been provided, the moneys within the fund of that county may be used to pay the costs of securing such services.

(b) Notwithstanding subdivision (a) or the limitations of Section 99231, during a period of up to five years that the San Francisco Bay Area Rapid Transit District is planning any extension of its system into a county outside of the district but with a coterminous boundary with the district and which contains a major transportation facility belonging to another county or city and county, the Metropolitan Transportation Commission may order that any funds in the local transportation fund of such county that are not necessary to pay approved claims under Article 4 (commencing with Section 99260) of this chapter be retained.