Cal. Business and Professions Code § 7470.16

(a) When a sectoral agreement is in effect, any TNC that is not a covered TNC for purposes of Section 7470.5 may choose to become bound to the sectoral agreement by providing written notice to the board, the certified driver bargaining organization, and the covered TNCs. A TNC that chooses to become bound to a sectoral agreement pursuant to this section shall be bound for the remaining term of the agreement. Such a TNC shall not, on account of its exercise of the option provided by this section, become a covered TNC for purposes of negotiation of subsequent sectoral agreements or coverage by subsequent sectoral agreements. (b) It shall be unlawful for any TNC that is not a covered TNC nor voluntarily bound by the terms of the sectoral agreement as provided by this section to make any statement, advertisement, or imply in any official communication that such TNC is bound by the terms of the sectoral agreement. (c) During the time that a noncovered TNC is bound by the terms of the sectoral agreement pursuant to this section, the certified driver bargaining organization shall represent the TNC drivers who drive for the noncovered TNC for purposes of this chapter. The noncovered TNC shall have the same obligations as a covered TNC to provide information to the board necessary to administer this chapter and to provide information to the certified driver bargaining organization necessary for representation of the TNC drivers.