Cal. Lab. Code § 4903.4

When a dispute arises concerning a lien for expenses incurred by or on behalf of the injured employee as provided by Article 2 (commencing with Section 4600) of Chapter 2 of Part 2, the appeals board may resolve the dispute in a separate proceeding, which may include binding arbitration upon agreement of the employer, lien claimant, and the employee, if the employee remains a party to the dispute, according to the rules of practice and procedure.