How much longer does it take to load/unload a freight train versus a truck? How much slower is the train and how longer does it take to ship? (and how does that affect cost or product quality when shipping items that must be refrigerated in transit?) Is it a realistic option for same-day or overnight shipping required for services like Amazon Prime in the volume that is currently being carried by trucks?
For items where delivery is not urgent, I'm all for using rail, but with expectations from consumers for quick delivery, its hard to see how they will be able to compete on the current system for rail-based freight.
An alternative (at least in the short-term), might be to create truck-only traffic lanes or highways with tolls and fewer exits. (and other lanes or highways just for cars) The lanes could be built to withstand the additional weight from the trucks, and non-truck traffic would run more efficiently and safely.