All decisions, orders and authorizations of the Public Utilities Regulatory Authority shall be in writing and shall specify the reasons therefor, shall be filed and kept in the office of the authority and recorded in a book kept by it for that purpose and shall be public records. Said authority may, at any time, for cause shown, upon hearing had after notice to all parties in interest, rescind, reverse or alter any decision, order or authorization by it made. Written notice of all orders, decisions or authorizations issued by the authority shall be given to the company or person affected thereby, by personal service upon such company or person or by registered or certified mail, as the authority determines. Any final decision, order or authorization of the Public Utilities Regulatory Authority in a contested case shall constitute a final decision for the purposes of chapter 54.