I hear the train a-coming

A friend links NPR's report on the Keystone XL rejection.
Among the alternatives to a pipeline - trains.
But the administration says there are ways of getting that oil to refineries in Texas without the Keystone XL, namely through “other new domestic pipelines, expansions or reversals of existing pipelines, and other modes of transport such as rail, that could play a role in increasing imports of crude oil from Canada to the United States, including to refineries in the U.S. Gulf Coast area.”
How long will the trains have to be to match the capacity of a pipeline.
And trains have to return north to pick up more crude. Do they go back empty?
I can't wait to hear about the carbon footprint of that idea.