Cal. Health and Safety Code § 18076

(a) Manufactured homes, mobilehomes, commercial coaches, or truck campers owned or leased by the United States, by any foreign government, by a consul or other official representative or any foreign government, by the state, by a political subdivision of the state, or by any city, county, or city and county, or public corporation shall be subject to registration under this code by the person having custody thereof, but shall not be subject to the registration fees specified in this code or the Revenue and Taxation Code, and that person shall display upon the manufactured home, mobilehome, commercial coach, or truck camper a decal bearing distinguishing marks or symbols which shall be furnished by the department free of charge. (b) Any manufactured home, mobilehome, or commercial coach purchased by a city, county, city and county, or any other public agency pursuant to the exception established in Section 18015.7 shall be subject to registration as specified in Section 18085, but shall not be subject to the registration fees specified in this code or the Revenue and Taxation Code. Application for registration shall be made to the department within 20 days from the date the transaction is completed. For purposes of this section, a transaction shall be deemed completed when the purchaser has signed a purchase contract or security agreement or paid any purchase price and has taken physical possession or delivery of the manufactured home, mobilehome, or commercial coach.