(a) Parties are encouraged to communicate and exchange information informally, including by telephone or by meeting, and to use the formal procedures provided for below only as necessary.

(b) Material or information provided by one party to another through informal discovery need not, for that reason alone, be made available to third parties. Nevertheless, no party may refer to, introduce into evidence, or otherwise use at a hearing, except in its prefiled written testimony or in response to cross-examination, any information obtained through informal discovery unless that party first shows that all other active parties received or had a reasonable opportunity to receive that response reasonably in advance of the hearing at which such use is proposed.