The Assistant General Counsel, Chief, Division of Operating Subsidy Contracts, shall be a party to all proceedings involving operating-differential subsidy contracts. The Assistant General Counsel and his representatives shall be designated as Public Counsel and shall be served with copies of all papers, pleadings, and documents in such proceedings. In addition the General Counsel may designate any member of his staff to serve as Staff Counsel in contract appeal cases or any other proceeding governed by the regulations in this part. Public Counsel or Staff Counsel shall participate in any proceeding to which he is a party, to the extent he deems required in the public interest, subject to the separation of functions required by section 5(c) of the Administrative Procedure Act.