Canadian National Railway Co (CNR.TO) on Saturday again urged Unifor, the union representing 4,800 of its mechanical, clerical and intermodal staff, to agree to binding arbitration and renewed its threat to lock out those workers on Monday. Canada’s No. 1 railway had called for binding arbitration on Friday when it first announced it was preparing to lock out employees represented by the union. Unifor, which on Friday called for CN Rail to return to the bargaining table, said on its Twitter feed on Saturday that the railway should negotiate a deal rather than seek arbitration.