You're all missing the big picture here though. Under the current integrated rail oligarchy, there is no market-based incentive to lower shipping costs to rail users. Railroads can and are simply passing on the costs of fuel to the shippers - so what reason is there to go with a coal-fired locomotive?

Now, if we had some form of competitive access to the US rail grid, then you would see more than token attempts to lower operating costs via cheaper fuel sources.

Electrification will only happen if the government subsidizes it.

One reason I believe CTL will occur is that there is a huge non-rail market for that alternative diesel fuel source. The railroads will use what the truckers use for fuel by default.