TORONTO/GATINEAU, Quebec (Reuters) – Canada’s biggest railway reached a last-minute tentative agreement with one of its unions on Monday, averting a lockout that threatened to delay imports from Asia and compound a U.S. West Coast port logjam. Canadian National Railway Co (CNR.TO) and Unifor, the union representing its 4,800 mechanical, clerical and trucking workers, struck a deal just before the railway’s 11 p.m. EST Monday deadline to lock out the workers.