The agency or its designated subordinates may, and on request of any party to a case shall, issue subpoenas requiring testimony or the production of books, papers, and physical or other evidence. Any person so subpoenaed who objects may, if the agency does not quash or modify the subpoena at his timely request as illegally or improvidently granted, immediately procure by petition a decision on the validity thereof in the circuit court as provided in § 2.2-4003; and otherwise in any case of refusal or neglect to comply with an agency subpoena, unless the basic law under which the agency is operating provides some other recourse, enforcement, or penalty, the agency may procure an order of enforcement from such court. Depositions de bene esse and requests for admissions may be directed, issued, and taken on order of the agency for good cause shown; and orders or authorizations therefor may be challenged or enforced in the same manner as subpoenas. Nothing in this section shall be taken to authorize discovery proceedings.