Notwithstanding the lack of a statute, charter or ordinance provision for the mailing of notice of hearings, each special assessment hearing heretofore held is validated insofar as any notice of hearing is concerned, if notice was given by mail to the owners or parties in interest whose names appeared at the time of mailing on the last local tax assessment records. Any such special assessment hearing is also validated as to any owner or party in interest who has actually received notice of hearing, has waived such notice, or has paid any part of the special assessment.