Hmm...
According to the WSJ article, the same number of BTUs from diesel cost about $4 now versus about 50 cents from natural gas at current industrial prices.
Even with locomotive conversion and natural gas liquifaction costs, looks like there could be plenty of margin for this to work.
After all, if NG is so much cheaper than coal for power plants (plus lower CO2 emissions), then it should be somewhere between “possible” to “very likely” that it will work for the big prime movers in locomotives.
It is definitely worth testing.
There is a lot more in play than mere nominal fuel cost. Engine longevity, for one (Diesel-cycle engines often outlast Otto-cycle engines). Different maintenance requirements. Different (and more dangerous) on-board fuel storage and delivery requirements. More extensive electrical systems due to the need for spark plugs to ignite fuel.
This is the wrong place to talk of carbon dioxide emissions in the context of their being a bad thing.
Natural gas is not cheaper than coal for power plants. Why do you think the European countries that have abandoned nuke power are switching to coal?
BNSF already boasts that they can move 2,000 pounds of freight a distance of 495 miles on one gallon of diesel.