this said, wargaming railway is a challenging attempt beyond the usual artillery range/MG effect "suspension of disbelief" issue, but I find it very interesting and rewarding if one is open to go beyond the usual wargaming conventions 8)
plus the size - I would assume Your whole set is at least 60cm long - take normal vehicle movement rules and calculate how many rounds it takes until the whole train is on the table if You start off-table. This of course depends on the speed. Now calculate how many rounds it takes to brake it down to standstill (considering realistic movement rules of course).
You end up either rushing over 2.5 m of tabletop in 2 rounds or deploying the train immobile as a terrain piece.