Within ten days following a request by the agency, the employer shall submit to the agency a list containing the names and last known addresses of all of the employees in the bargaining unit described in the petition. Following administrative determination that the petition is supported by a sufficient showing of interest, the agency shall furnish a copy of the list of names and addresses to the petitioner. Following granting of a motion for intervention, the agency shall furnish a copy of the list of names and addresses to the intervenor.