The Commission may issue subpoenas and order discovery in aid of investigations and hearings under this part. Witnesses subpoenaed by the Commission to testify in any proceedings under this part are entitled to the same witness and mileage fees as witnesses in proceedings before any circuit court in the State. The party who requests that a witness be subpoenaed to testify in a proceeding shall pay the fees or, if the party is unable to pay, the Commission shall pay the fees.