Sts. & Hy. Code, § 5895.50

Whenever the property, which fronts on an area where improvements are required to be constructed pursuant to the provisions of this chapter, lies entirely or partially within a city or unincorporated territory of a county and the improvement area or portions thereof lie 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 all or a portion of the area to be improved 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, notwithstanding the fact that the property fronting on the improvement area lies entirely or partially within another city or unincorporated territory of another county.