California Code, Revenue and Taxation Code - RTC § 1754

(a) The county clerk of the county where the appeal originated shall be designated as the lead clerk for the purposes of scheduling a hearing on an appeal before the board and coordinating with the county clerks of each participating county, unless the participating counties appoint a single county clerk to serve as the lead clerk for the multijurisdictional assessment appeals board.

(b) If the participating counties appoint a single county clerk to serve as the lead clerk for the multijurisdictional assessment appeals board, the agreement between the participating counties shall provide for the allocation of costs and reimbursements associated with the activities of the board among the participating counties.