Yes, the B&T was standard gauge, but the Rio Grande Western was narrow gauge for a few years, and I assumed that the old wooden boxcar in Thompson might be narrow gauge, so that's why this thread is up here.
There is very little that I could find about the B&T, and Sego for that matter, in the local Utah libraries and historical societies. It may have been that it was narrow gauge at one point early in its history, although I think the RGW was already standard-gauged by that time.
I'm still trying to figure out if the RGW narrow gauge ever really reached Ogden as some people have told me...