Cal. Civ. Proc. Code § 1263.270

Where an improvement pertaining to the realty is located in part upon property taken and in part upon property not taken, the court may, on motion of any party and a determination that justice so requires, direct the plaintiff to acquire the entire improvement, including the part located on property not taken, together with an easement or other interest reasonably necessary for the demolition, removal, or relocation of the improvement.