A spill would not so much impact the mountains as the waterways.  CN has a technique in the works to transport oil as a semi-solid, which would be easy to clean up and would not be a lac megantic tragedy in waiting. (It would not be highly flammable.)  The mode of transportation should suit the product, not the other way around.
I expect the pipeline will go through, but I hope common sense will prevail and it won't terminate in  heavily populated Burnaby.