29 C.F.R. § 4221.10

(a) Witnesses. Each party to the dispute shall bear the costs of its own witnesses.

(b) Other costs of arbitration. Except as provided in § 4221.6(d) with respect to a transcript of the hearing, the parties shall bear the other costs of the arbitration proceedings equally unless the arbitrator determines otherwise. The parties may, however, agree to a different allocation of costs if their agreement is entered into after the employer has received notice of the plan's assessment of withdrawal liability.

(c) Attorneys' fees. The arbitrator may require a party that initiates or contests an arbitration in bad faith or engages in dilatory, harassing, or other improper conduct during the course of the arbitration to pay reasonable attorneys' fees of other parties.