We are all (understandably) very railway-centric on here, but we need to take a step back away from the nostalgic aspects of it and think 'why does the military need a railway capability'. When was a railway last important to the outcome of a conflict? If you think about it, in the world of palletisation/containerisation, helicopters, HGV's and heavy lift transport aircraft that can use short, rough runways, railways are just a liability in a hostile environment. They take a lot of defending and are easily interfered with. If someone blows up one railway bridge on a line, it could be out of use for weeks. If someone blows a road-bridge it can be fixed, bypassed or replaced with a temporary solution within hours. Locomotives and rolling stock costs millions, one lorry is relatively expendable.