California Code, Public Utilities Code - PUC § 105051

The Counties of Marin and Sonoma, the Golden Gate Bridge, Highway and Transportation District, or any other public agency may render assistance to the district as it may require, including the performance by officers of the counties, the Golden Gate Bridge, Highway and Transportation District, or other public agency of the functions of legal counsel, controller, auditor, and treasurer.  The district shall reimburse the counties, the Golden Gate Bridge, Highway and Transportation District, or other public agency for the services performed by them for the district.