Cal. Gov. Code § 4529.11
All projects included in the State Transportation Improvement Program programmed and funded as interregional improvements or as regional improvements shall be subject to Article XXII of the California Constitution. The sponsoring governmental entity shall have the choice and the authority to contract with qualified private entities for architectural and engineering services. For projects programmed and funded as regional improvements, the sponsoring governmental entity shall be the regional or local project sponsor. For projects programmed and funded as interregional improvements, the sponsoring governmental entity shall be the State of California, unless there is a regional or local project sponsor, in which case the sponsoring governmental entity shall be the regional or local project sponsor. The regional or local project sponsor shall be a regional or local governmental entity.
Ca. Gov. Code § 4529.11