Cal. Civ. Proc. Code § 1260.030

(a) If there is a dispute between plaintiff and defendant whether particular property is an improvement pertaining to the realty, either party may, not later than 30 days prior to the date specified in an order for possession of the property, move the court for a determination whether the property is an improvement pertaining to the realty.

(b) A motion under this section shall be heard not sooner than 10 days and not later than 20 days after service of notice of the motion. At the hearing, the court may consider any relevant evidence, including a view of the premises and property, in making its determinations.