Long before the war, the lands of Equestria were knitted together with a blanket of steel rails and wooden cross-ties, tracks that stretched to connect every major and minor settlement across the country. Even after the destruction wrought by the balefire bombs and megaspells, the tracks that tied Equestria together remained vital, and as the world recovered from the apocalypse the technologies needed to bring such a massive form of transportation and communication came with it. While the trains that ran following the megaspells rarely carried similar cargo to those that ran prior, the payments for the irreplaceable service still flowed, for better or worse. Those who held strong objections to hauling the newer commodities of a post-apocalyptic world rarely lasted long in the railroad business, and even for those who managed to avoid pulling those trains, it's most always ultimately delaying the inevitable...
-----
Set during roughly the same canon as Gamma Deekay's Fallout Equestria: Long Haul, recommended reading to understand a few of the nods and moments seen, and a few locations as well!