I saw a BSA road bike at the thrift store once. I went back and forth about whether to buy it (pros: collector's item, cons: weighed about 50 lbs and needed a lot of work). In the end I kicked myself for not buying it because I called a guy who collects BSA stuff and he offered me about $800 for it. I went back to the store and it was gone. (I didn't make the same mistake when I found a swing bike there later; I bought it not knowing what it was but that it could have some collector value to someone). It was a ten speed and had a disk brake in the rear (which I thought was interesting since the bike was probably like 30 years old or so). So, it wasn't a track bike, but that is my experience with BSA bikes. I think they're quite rare as the guys at the museum I called had never before seen a bike made by Boy Scouts (which I assume is what you're talking about when you say BSA, if not regard everything I just said).