Cal. Streets and Highways Code § 859

In the event that such changed grade of a State highway fails to meet the grade of any intersecting or intercepting highway, the department is authorized and directed, at the same time, to do such work as is necessary in order to cause such intersecting or intercepting highway to meet the State highway at grade and to restore it to its previous condition of surface, as near as may be. The procedure set forth in this article for the change of grade of the State highway in a city may be followed as to the portion of such intersecting or intercepting highway, the grade of which is changed. In lieu of, or in addition to, the above procedure mentioned in this section, the department and the governing body having jurisdiction over any such intersecting or intercepting highway may enter into a cooperative agreement in respect to the doing of any work authorized by this article, or the taking of any action in respect to such intersecting or intercepting highway as may be authorized by law.