Yes it is possible, FactCheck.org says so:
Can a freight train really move a ton of freight 436 miles on a gallon of fuel?

Yes.

Some rail lines do better. The Soo Line, which is the U.S. branch of the Canadian Pacific, operating in the upper Midwest, reported moving each ton of freight 517.8 miles per gallon of diesel fuel, on average. Lines operated by the Grand Trunk Corp. reported 510.5 ton-miles per gallon.

The national average figure of 436 miles is the highest on record, according to AAR, and a 3.1 percent increase from the 423-mile figure reached in 2006.

The rail industry says its fuel efficiency has increased by 85 percent since 1980. It attributes that to factors that include using new and more efficient locomotives, training engineers to conserve fuel, using computers to assemble trains more efficiently in the yard and to plan trips more efficiently to avoid congestion, and reducing the amount of time engines are idling.