I'm not convinced TOR is a good workaround - If you wanted to test a system like webwise, then it seems to me a free public proxy or a TOR exit node where you would find lots of "volunteers" could be a good place to start.
The javascript leaks from the 2006 tests contained a variable that appeared to indicate the ISP, and one of the plain text ones that cropped up was "PUBLICPROXY".
See the javascript in this forum post:-
http://www.teens411.com/forum/forum_posts.asp?TID=971