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.
Yes it is, and higher efficiency as well (combined cycle gas turbine/steam turbine).
"Why do you think the European countries that have abandoned nuke power are switching to coal?"
Uh, perhaps because they HAVE domestic sources of coal but IMPORT natural gas (from the Russki's). And because they are behind the curve on horizontal drilling and fracking.