At the end of 2007 coal had risen to a price of $36.07 per ton or $1.82 per million btu. So natural gas is 2.64 times more expensive than coal.
Now a coal car, is a real pain in the butt, because you need a coal tender, and it is hot and dirty and there are not many coal stations along the highways, so travel by coal car may not be practical.
Nothing cheaper than coal per BTU, that’s for sure.