Iowa Admin. Code r. 621-2.4
Any interested person may request intervention in any proceeding before the public employment relations board. An application for intervention shall be in writing, except that applications made during a hearing may be made orally to the hearing officer, and shall contain a statement of the reasons for such intervention. When an application for intervention is filed regarding a petition for bargaining representative determination, 621-subrules 4.3(2), 4.4(4), 5.1(2), 5.5(2), and 5.5(4) shall apply.
Where necessary to achieve a more proper decision, the board or administrative law judge may, on its own motion or the motion of any party, order the bringing in of additional parties. When so ordered, the board shall serve upon such additional parties all relevant pleadings and allow such parties a reasonable time to respond thereto where appropriate.
Iowa Admin. Code r. 621-2.4