75 Pa.C.S. § 6149: Automatic reciprocity.

If no agreement, arrangement or declaration is in effect with respect to another jurisdiction as authorized by this subchapter, any vehicle properly registered or licensed in the other jurisdiction, and for which evidence of compliance is supplied, shall receive, when operated in this Commonwealth, the same exemptions, benefits and privileges granted by the other jurisdiction to vehicles properly registered in this Commonwealth with the same type of registration.