4000 tons/day is a nice round number. If they are only hauling chrome, that works to 5 trains a week, or 7 trains if they are hauling nickel concentrate on contract from NOT facility. 4000 t/day also translates to 1.2 m ton/year, which is about the NA market consumption. With 4000t/day a railline is probably going to be feasable.
Interesting thoughts are starting to work their way to the surface.
Regards
K