It's a very complex issue. The railway companies in Canada have what is called common carrier obligations. The law prescribes railway companies to accept freight that is offered to them for carriage, and they're supposed to carry the freight that the shipper provides at a certain fee, which they establish on a commercial basis. It would be difficult to suggest that the railways can pick and choose what they carry, or the government prescribes what the railways will carry.
On May 15th, 2014. See this statement in context.