The oil is going to be processed anyway, whether it goes south or east.  Pipelines are merely a transport vehicle.  Greenhouse gases should not be a factor on pipelines.

With eastern refineries processing imported oil brought in from oil tankers from another continent, doesn't it make more sense for them to process Canadian oil?  Imagine the greenhouse gases from the oil tankers as they traverse the oceans.  How much greenhouse gas could have been avoided using pipelines from out west?