But Bill -

It will probably take about the same amount of diesel fuel to pump it through the pipe as to haul it by rail.

And since it's unrefined at the end where it needs the biggest push, they'll have to bring in refined diesel by rail or by truck in order to have any at the pump where they need it, or build a local refinery just to run the pump.

I'm not up to date on the latest practices, but pumping it through the pipe will require a number of "booster stations" spread along the pipeline. Practice a few years back was about 50 to 75 miles between boost pumps for heavy fluids, so about 20 pumping stations along the route(?).

Each of the booster stations is a stationary and pretty much constant polluter, about like running the train at full power 24/7 inside the station (?). The train (or trucks) can bring their own fuel and they just "pass through" so that there's less concentrated local accumulation of pollution, with time for some dispersal between trips. Take you pick on which you think is better with respect to the tailpipe effects.

John