(a) If notice of a hearing on a petition is required and, except for specific notice requirements as otherwise provided, the petitioner shall cause notice of the time and place of hearing of a petition to be given to any interested person or his attorney if he has appeared by attorney or requested that notice be sent to his attorney. Notice must be given:

(1) by mailing a copy of the notice at least twenty days before the time set for the hearing by certified, registered, or ordinary first class mail, or by a commercial delivery service that meets the requirements to be considered a designated delivery service in accordance with 26 U.S.C. § 7502(f)(2) addressed to the person being notified at the post office address given in his demand for notice, if any, or at his office or place of residence, if known;

(2) by delivering a copy of the notice to the person being notified personally at least twenty days before the time set for the hearing; or

(3) if the address or identity of any person is not known and cannot be ascertained with reasonable diligence by publishing a copy of the notice in the same manner as required by law in the case of the publication of a summons for an absent defendant in the court of common pleas.

(b) The court for good cause shown may provide for a different method or time of giving notice for any hearing.

(c) Proof of the giving of notice shall be made on or before the hearing and filed in the proceeding.

(d) Notwithstanding a provision to the contrary, the notice provisions in this section do not, and are not intended to, constitute a summons that is required for a petition.