(a) Whenever a person is involved in a proceeding before the administrator, and an attorney at law has filed a notice of appearance for such person in such proceeding, all subsequent written communications or notices to such person (other than subpoenas) shall be sent to such attorney at law at the address designated in such notice of appearance. The notice of appearance to be filed by an attorney at law who represents a party in a proceeding before the administrator shall be on a form prescribed by the administrator, unless proceedings are instituted before the administrator by formal application pursuant to these regulations and the representation of such attorney at law and his mailing address are stated in such application in the space allotted for the mailing address of the represented party. The service of written communications and notices upon such attorney at law shall be deemed full and proper service upon the party or parties so represented.

(b) Whenever an attorney at law shall represent the same party or parties in more than one proceeding before the Division of Housing and Community Renewal, separate notices of appearance shall be filed in each proceeding. For the purposes of this section, a protest against an order of the district rent administrator shall be deemed a separate proceeding.

(c) This section shall not apply to preliminary investigations conducted by the administrator.