Practically all transit vehicles are shipped by road. I wondered why, but after a visit to Siemens some years back and a little observation it's clear why: few rail transit operations have connections with the national railroad system (BART's an exception, actually, but the connection isn't much of one suitable mainly for delivering rail and ballast; yes, there's a short bit of 3-rail track visible if you zoom in on the Google view
), so the shipment would have to be on a truck at some point anyway; the trucking is more trackable (active GPS all the way); more reliable and predictable (and faster) timing; and less likely to be damaged (other than by possible collisions along the way, though few have been reported). Yes, an 80' long car is an oversized load, but truckers and highway route planners have dealt with that for years; at least BART or light rail cars are seldom overheight.
That said, I think I've seen at least one Youtube with what looked like a shrink-wrapped light rail car going by on a flatcar, so it can happen. By far most of the shipping, though, is done by road.
Yes, I'm old enough to vaguely remember Muni getting some (part of the the St. Louis purchase?) PCC cars delivered by rail in the late 1950s, when SP still had an active track past Geneva Ave. That was a very, very long time ago, and shipping PCCs by road back then was a considerably more difficult proposition than it would be today.