California Code, Labor Code - LAB § 5273

(a) In disputes between an employee and an employer, the employer shall pay all costs related to the arbitration proceeding, including use of facilities, hearing reporter per diems and transcript costs.

(b) In all other disputes, the costs of the arbitration proceedings, including the arbitrator's compensation, shall be paid as follows:

(c) Disputes regarding the costs or fees for arbitration shall be within the exclusive jurisdiction of the appeals board, and shall be determined initially by the presiding judge of the district office.