I believe the Darjeeling route has been/is in process of being upgraded to run in TS2012 (Trainz). There's more on the "official" thread at N3V's forum. It's a crowning achievement of what can be achieved when a team of people devote themselves to reproducing a part of the world in great detail. If the route was ever made for Railworks I'm sure it would be equally as popular, but unfortunately at present the sim doesn't have much narrow gauge support.