Cal. Gov. Code § 55330

When the legislative body of a local agency and the legislative bodies of one or more cities or sanitary districts find and adopt a resolution declaring that it will be for the interests or advantage of the local agencies to do so, the legislative bodies may enter into a joint agreement authorizing the construction and maintenance of conduits or lines in, over, or along the streets or other public places of any of the local agencies, or in part outside of the limits of the local agencies, at their joint expense and for their joint use and benefit upon the terms and under the regulations approved by all of them.