Yep, Jones is correct. the best way to do it, if you were going to do it, would be to have an enclosed car, and the army's rail loading manual (I have one) You basically chock and strap a unit to the car, until you could turn the car upside down and shake it, and the item won't fall off. If you had a shortline at each end that would work with you, it could be done. All they would do is order the car (if you didn't have one) and you would still have to load it. And it could take weeks just going a few states over.
Yes, slack action. If you have a long enough train, with the right (or wrong?) type of equipment in it, and an inexperianced or noncaring engineer at the throttle, you can have the front end up to 10-15mph, and the rear sitting still. Then when the slack gets pulled out, each car is 'snapped' to 10-15mph, from a stand still. Not pretty and can really damage stuff inside. I've had a train 'pull apart' because of slack action.
I think you could do it, if you had a car that was in excellent shape, (or used the railroads, as they will fix their own car and not charge the consignee) a shortline at each end, and could strap the thing down really really good and didn't mind waiting on it a little while.
I own full size railcars, it gets EXPENSIVE to just have them moved from A to B. they will charge for every side move, and every little 'repair' they deem necessary. You can put a 'do not repair until owner is contacted' on the waybill, but they may or may not 'miss' that when they send you a bill for a couple of new axles and brake shoes...
With all the headaches involved, trucking is the better bet for moving MVs. And I hate to say that, being a railroader and all.