The insurance carrier is solely responsible for enforcing a subpoena to compel the appearance of the witness at the deposition. In the event that the insurance carrier fails to enforce a subpoena to compel appearance of the witness at the deposition, the report of the witness shall remain in evidence. For any such medical witness authorized by the Chair to treat or conduct independent medical examination of injured workers or both, the Board shall promptly direct the witness to appear at such deposition.