Cal. Veh. Code § 5003
The department shall maintain a record of the registration of exempt vehicles with regular series plates, which record shall not be open to public inspection. The record shall be disclosed in the event of any accident involving a vehicle so registered on demand of the Attorney General or upon an order of court. In the event of an inquiry by a county sheriff, city chief of police, or judge of any court relating to such exempt vehicle in connection with an alleged violation of state or local traffic laws, the department shall notify the supervisor of the person to whom the vehicle was assigned of the inquiry and the alleged violation and shall notify the inquiring official that this has been done without disclosing the name of the person involved.
Ca. Veh. Code § 5003