(1) Where it appears that a pending contested case will affect or determine the legal rights, duties, or privileges of a person or where the joinder of a party is needed for just adjudication under the provisions of Rule 19 of the Montana Rules of Civil Procedure, such person will be allowed to intervene as a party upon timely application or where such fact appears as of record.

(2) Where permissive intervention or joinder of a party would be permitted under the provisions of Rule 20 of the Montana Rules of Civil Procedure, such intervention or joinder may be allowed upon timely application and a lack of prejudice to the parties of record. Where intervention would delay the hearing or disposition of a contested case, duplicate contentions of a party, cause prejudice to a party, or where the interests of a party seeking intervention are adequately represented by a party of record, the commission or hearing examiner may deny intervention or joinder.

(3) The hearing examiner or the commission may permit a party who does not seek to intervene as of right to participate in a matter in a limited capacity, but not as a party. A person who may not seek intervention as of right may be permitted to participate in a contested case in a limited manner, such as a friend of the commission, where such participation would not cause prejudice to a party, delay proceedings or deny a fair hearing. In such instances, a limited participant shall not have the right to control proceedings.