Reply #4: Dunno. Depends on how much got ripped out.

[TheMadMonk]

Where the main lines still exist, I suspect it could be done in a few years, or less depending on how much manpower got thrown at the problem. Actual (re)construction of a small spur in every town (or at least semi-major centre, would take a month or two. Side loaders are all but off the shelf. Refitting cars for on the fly decoupling/coupling no more than 12 months to develop, and another year to put into mass production.

The biggest hurdle would be completely separating the road network (and the idiots who drive into trains) from the rail.