California Code, Streets and Highways Code - SHC § 5895.51

Whenever a block, on which improvements are required to be constructed pursuant to the provisions of this chapter, lies within a city or unincorporated territory of a county and within one or more other cities or unincorporated territory of one or more other counties, the superintendent of streets of any city or county having jurisdiction over a part of the block shall have full authority to serve notices, to construct, and to do all work contemplated by Article 2 (commencing with Section 5875) and Article 3 (commencing with Section 5890) of this chapter in that portion of the block lying in the territory of another jurisdiction after the superintendent obtains consent from the legislative body of that jurisdiction.

The consent of the legislative body shall be given by resolution adopted by a majority vote of the body's membership. Thereafter, except as provided in Section 5895.54, the city or county whose superintendent of streets obtained the consent shall have jurisdiction over such areas for the purpose of sidewalk or curb construction.