Any person may file an application for leave to intervene in a proceeding, which application shall show a statutory right or a substantial interest in the proceeding. A person permitted to intervene in a proceeding thereby becomes a party to the proceeding for all purposes. No decision granting or denying intervention shall be deemed to constitute an expression of the Division with respect to the substantive right of the intervenor.
Ill. Admin. Code tit. 92, § 14.1155