(a) Witnesses who are not employees or former employees of the federal government shall be paid the same fees and mileage as paid for like services in the District Court of the United States where the subpoena is returnable, except that expert witnesses shall be paid a fee not to exceed the local customary fee for such services.

(b) Where OWCP asked that the witness submit evidence into the case record or asked that the witness attend, OWCP shall pay the fees and mileage. Where the claimant asked for the subpoena, and where the witness submitted evidence into the record at the request of the claimant, the claimant shall pay the fees and mileage.