TORONTO (AP) — A workers union and Canada’s two major freight railroads wrapped up a nine-hour arbitration hearing with the Canada Industrial Relations Board. But there was no decision Friday on whether the board would order one of the railroads back to work following a potentially devastating stoppage. The Teamsters Canada Rail Conference filed a 72-hour strike notice Friday morning against Canadian National, while the trains continue to run. Workers at Canadian Pacific Kansas City went on strike on Thursday. The government forced the companies and the union into arbitration. The union plans to challenge the arbitration order and questions whether the industrial relations board has the authority to order them back to work. But the Teamsters said they would follow the board’s order.