(a) This article applies in an adjudicative proceeding required to be conducted under Chapter 5 (commencing with Section 11500).
(b) An agency may use the subpoena procedure provided in this article in an adjudicative proceeding not required to be conducted under Chapter 5 (commencing with Section 11500), in which case all the provisions of this article apply including, but not limited to, issuance of a subpoena at the request of a party or by the attorney of record for a party under Section 11450.20.