For significant volumes, shipment by pipeline is FAR cheaper than by rail.
About half the oil we get from Canada is already from the oil sands.
It would create good paying jobs in America and help to revive our stagnant economy.
You would think Obama would be doing everything to expedite this project.
Pipelines cost a lot to build — that capital cost has to be amortized over the life of the pipeline, or over the supply of commodity being shipped (whichever comes first).
In the case of the Alberta oil sands; CN rail already has track in place from Alberta to the west coast. There is plenty of excess capacity, in this railway, to handle millions of barrels of oil/day.
Pipelines take time to build. Building tanker cars takes a lot less time — and it is scalable. That means quick response, and little risk.
A new pipeline would be strongly opposed by environmentalists (just as the proposed one to Texas is being opposed). The railway is already in place. There would be opposition from environmentalists, but their hand would be much weaker. Environmentalist roadblocks (as opposed to real environmental concerns, which would be addressed); would be the main impediment to building a pipeline.
Environmentalists here also strongly oppose shipping oil, from a west coast port. So far, they seem to be winning. If the choice were between building a port facility, and completely shutting down the Alberta oil sands — the port would likely be built. (Recall that environmentalists want all the oil-sands production to stop — and that Obama leans in that direction.)
That said, the best thing for North America would be to build the pipeline down through the US. However, that seems to be up to the U.S.A.
Here's a couple of short articles about the use of rail to ship oil from the oil-sands. The first one mentions shipping raw bitumen to China, where it would be refined. The bitumen would have to be heavily diluted, and heated, to pass through a pipeline.
http://www.cjob.com/Channels/News/Edmonton/story.aspx?ID=1351872