Those cars, along with all the equipment (mostly standard gauge) was collected by Charles Bovey. Aside from referring you to the webiste that James Maxwell listed above, Mr Bovey was very well connected when he went looking for railroad equipment in the 60's.
The passenger cars are all of Soo Line parentage, except the end observation, which was a former GN business car A4 (lst). There is also a modern GN business car (A3 (2nd),donated directly from service--with the interior virtually untouched from then and Milwaukee Road business car #999. There are also four Westside Lumber flatcars, among other things.
The prospects of this equipment pretty much ride on what people can do for it. I originally became involved with the operation because I wanted to work on the equipment collection. Of course I wound up in train service (which is a blast) and trying to get into engine service.
As alluded to above, changes are in the works, and it appears the Montana Heritage Commission and the FOC&TS may well develop a good working partnership. Beyond that, I can't add much at this point, but feel free to come and visit. Be forewarned, it is entirely possible that there will be no operations on Memorial Day. If you are planning a visit at the time, call ahead to find out what is running.
Look forward to seeing you!
Michael Seitz
Switchman, Alder Gulch Shortline
Missoula MT