24.1.6  Parties to the proceeding.  The parties to any proceeding pursuant to this rule shall be the board and the petitioner.  Any other person may seek leave of the board to intervene in such a proceeding, and leave to intervene will be granted at the sole discretion of the board.  A petition to intervene shall set forth the same matters as required by Rule 24.1.4.  Any reference to a "petitioner" in this rule also refers to any person who has been granted leave to intervene by the board.