Procedure concerning added parties

(a) During hearing. In addition to the designation of parties in the initial notice and in response to petition, the commissioners may add parties at any time during the pendency of any hearing upon their finding that the legal rights, duties or privileges of any person will be determined by the decision of the commissioners after the hearing or that the participation of such person as a party is necessary to the proper disposition of the contested case. (b) Notice of designation. In the event that the commissioners name or admit any party after service of the initial notice of hearing in a contested case, the commission shall give written notice thereof to all parties theretofore named or admitted. The form of the notice shall be a copy of the order of the commissioners naming or admitting such added party and a copy of any petition filed by such added party requesting designation as a party. Service of such notice shall be in the manner provided in these rules.