If i have read the posts correctly then the track, camber and/or castor will not make any difference as the wear is only on one tyre and not both......
This would suggest a worn suspension bush or a broken coil spring on one side (The side with the worn tyre).
Now if my memory serves me right you drive a E36 BMW ? If so then the rear suspension bushes are prone to collapse (Especially if wheelspin's/drifting/erratic drivig) so i would get these checked thoroughly. They are infront of your rear wheel just on the inside of your sill area.
I would post a picture for you but i have forgotten how too..... Now thats really bad !
If it were camber/castor then typically both rear tyres would wear down. Hope this helps you ? If your stuck you know where i live, feel free to pop in for a cffee and i will have a look for you.