Cal. Sts. & High. Code § 31153

The authority may provide in the proceedings authorizing the issuance of bonds, or may otherwise agree with the purchasers of bonds, regarding the deposit of all money constituting the Acquisition and Construction Fund and the Toll Revenue Fund, and may provide for the deposit of such money at such times, with such depositaries or paying agents, and upon the furnishing of such security as may meet with the approval of the purchasers of the bonds. The depositaries and security provided for or agreed upon, however, shall be qualified and eligible in accordance with law.