For section 521 proceedings, this section shall apply in lieu of § 18.10 of this title:

(a) The term “party” wherever used in these rules shall include any person that is a subject of the temporary order and is challenging the temporary order under these section 521 proceedings, and the Secretary. A party challenging a temporary order shall be designated as the “respondent.” The Secretary shall be designated as the “complainant.”

(b) Other persons shall be permitted to participate as parties only if the administrative law judge finds that the final decision could directly and adversely affect them or the class they represent, that they may contribute materially to the disposition of the section 521 proceeding and their interest is not adequately represented by the existing parties, and that in the discretion of the administrative law judge the participation of such persons would be appropriate.

(c) A person not named in a temporary order, but wishing to participate as a respondent under this section shall submit a petition to the administrative law judge within fifteen (15) days after the person has knowledge of, or should have known about, the section 521 proceeding. The petition shall be filed with the administrative law judge and served on each person who has been made a party at the time of filing. Such petition shall concisely state:

(1) Petitioner's interest in the section 521 proceeding (including how the section 521 proceedings will directly and adversely affect them or the class they represent and why their interest is not adequately represented by the existing parties);

(2) How his or her participation as a party will contribute materially to the disposition of the section 521 proceeding;

(3) Who will appear for the petitioner;

(4) The issues on which petitioner wishes to participate; and

(5) Whether petitioner intends to present witnesses.

(d) Objections to the petition may be filed by a party within fifteen (15) days of the filing of the petition. If objections to the petition are filed, the administrative law judge shall then determine whether petitioners have the requisite interest to be a party in the section 521 proceeding, as defined in paragraph (b) of this section, and shall permit or deny participation accordingly. Where persons with common interest file petitions to participate as parties in a section 521 proceeding, the administrative law judge may request all such petitioners to designate a single representative, or the administrative law judge may designate one or more of the petitioners to represent the others. The administrative law judge shall give each such petitioner, as well as the parties, written notice of the decision on his or her petition. For each petition granted, the administrative law judge shall provide a brief statement of the basis of the decision. If the petition is denied, he or she shall briefly state the grounds for denial and may consider whether to treat the petition as a request for participation as amicus curiae.