(1) Any labor organization, employee, or group of employees may file a petition to intervene within seven days of the first day of posting of the notice of unit determination proceedings.
(2) The petition shall be accompanied by proof of interest, consisting of authorization cards, or copies thereof, from at least ten percent of the employees in the unit. The cards shall indicate the signatories' choice of exclusive representative.
(3) The petition to intervene shall conform in all other respects to the requirements for a UD petition.
(4) The board agent shall review the petition and the authorization cards for compliance with these rules and serve a copy of the petition to intervene upon all other parties.