Thanks for the tips so far, guys.

Yeah, I'd temporarily forgotten about looking at topo maps. There are some decent (albeit old) maps on
topozone.com, and the
California Spatial Information Library has some decent digital raster graphics (DRGs) as well: they're pretty much plain topo maps, only georeferenced to load in a GIS. I think I do have 1 m elevation data on my computer, but I'll get that out when I need to use it.
TIGER is only about 1:100k scale, yeah, so it's definitely not the most accurate for the scale that I'm working at (obviously). I've been trying to plot - as best I can - the coordinates of the track using Google Earth and the lat/long reader on the DLS (setting the world origin in Surveyor as accurately as I can), and that seems to work fairly well. Though as someone mentioned in another thread, there will be distortion when going from a geographic coordinate system (Google Earth) where the world is assumed to be spheroid, into Trainz, in which I presume the "world" is assumed to be a flat board. We'll see how that goes.
Being a GIS specialist for a living comes in handy in my hobby time too, it seems.
I didn't know about the Railroad Timetable thingys, so that's something to look into. I'd thought about shooting off an e-mail to Union Pacific, too, but I haven't got around to that just yet.
Thanks for all your help so far, guys.
~Nathan