Tim,
Golf course dirt is usually $2-3, as TD alludes, but can be different, since bid forms have a separate number for "shaping" after the dirt is hauled and placed. That usually absorbs some of the cost which might not be the case in your engineers bid form.
Other factors might be the compaction spec for a railroad, the length of haul (rarely more than 1500 feet on a golf course, with most of it less than 1000 feet) and "other specifications." We don't know the cost of bonds, insurance, environmental mitigation, etc. We also don't know the amount of testing or inspection, etc. I am guessing that those costs (which make Don Mahaffey cringe!) are driving the high price.
It could also just be that just as consultants charge way more per hour when they go in as expert witnesses, because they know the legal system is used to it, that the bidders all know (as they once did with golf) that the railroads and oil companies are both doing quite well right now hauling oil, and the general pricing level has simply risen to what the market will bear.
I can tell you GC contractors (and architects....) bid less now than in the heyday, and materials have gone up, so it all came out of the "what the market would bare" portion of the cost.