Except as provided in § 2414.6, ex parte communications prohibited by § 2414.2 shall include:

(a) Such communications, when written, if copies thereof are not contemporaneously served by the communicator on all parties to the proceeding in accordance with the provisions of part 2429 of this chapter; and

(b) Such communications, when oral, unless advance notice thereof is given by the communicator to all parties in the proceeding and adequate opportunity afforded to them to be present.