A shack is presumably just a term for a little railway station with minimal buildings/staffing/facilities, primarily in the expression "all shacks"? Or am I missing something here?
Something nobody has yet mentioned is that when you have one locomotive on each end of a train, it's called "top and tail". So there's your "tail" expression, though not in the same place as "head" oddly enough!
Distance between two stations, as well as the "absolute" distances from a fixed point, are both usually referred to as mileage. Chainage is also sometimes used (80 chains in a mile, 22 yards in a chain), especially if the distance is likely to be on the order of magnitude of chains. Kilometreage I've occasionally heard, though this tends to be less common, for things like the London Underground and other metro systems that use metric. I'd probably just say "mileage" even though it's inaccurate.
I've also heard the term standage but I believe this is primarily used for shorter distances — things like the lengths of sidings/platforms, etc. I've not heard it be used for anything that would be measured in miles.