Earl you are correct. Much of the dubbed stuff sounds crappy, and most is not the right railroads. The stuff we did on the Rayonier, Canadian, DM&IR, etc had authentic audio done when the films were shot. Not 100% matches cause sometimes there was no audio done on a scene, and other times the guy had great audio at night. But in one of the Canadian shows, I matched perfectly about 50% of the show, and the other 50% I used sounds at similar speeds with same class engines. When I say we had 50% exact, the audio was for the film we were watching. In one scene at Portage La Prairie, a pair of 2400 series 4-6-2's is switching some cars for its freight and each engine whistled 4 times as it headed back to the train. I matched that perfectly with the film and audio. In another scene a CPR Royal Hudson was running out its last year in freight service. The audio was about 2-3 minutes long, but the film clip crossing the CN diamond was about 30 seconds. So I put in a freeze frame of the engine before we saw the film, and ran extra audio under it, to hear the whistle, and then dissolve into the film with the audio matched. It was fun stuff to work with. I bought all those reels from Elwin Purington cause he realized how big of a job it would be to work on it. I had it all transfered to DAT. Jim Gunning worked on "Sweeting" about an hour or more CP AND CN audio from those films, but we never did anything with the cd for some reason. Maybe it was a matter of doing the notes, I don't remember.
As for NG audio, the old Rio Grande would be the easiest to dub the sound since most of the stuff is still running. It would be easy to fake it with new audio, but I have no idea what those whistles sounded like in the films, or other scenes. To me the vintage stuff is all about the images. Far more black and white stills, and color slides were taken than films back in those days, so seeing the stuff moving is special. To me the audio is secondary. My dad used to say "We watched the stuff on our home projector and were happy to watch them". Nobody worried about sound, but enjoyed seeing the stuff moving.
I have heard some folks complain about dubbed audio on diesels as well. Wrong engines and horns and so forth. Nothing is perfect I guess.
Greg