The automobile protection agency has some winter tire ratings, but they just give a brief summary of the tire and their opinions. No factual information (testing) is available. And the tires listed may be out of date (they still have Blizzak WS-60s instead of WS-70).
http://apa.ca/tire_wintertireratings.aspConsumer reports sometimes has winter tire rankings - I have a truck winter tire ranking but it is from 2008. Maybe there is something newer?
I doubt you'll find any better tests (in terms of sample size, reproducibility, and thoroughness) than those done by tirerack. I've ordered winter tires from them twice, and phoned them as well for advice (WS70s vs Continental winters vs X-Ice). The service has been uniformly excellent. Too bad about the shipping fees & brokerage - but the end price was still highly competitive.
I also enjoy the winter tirereviews from autos.ca, but as you mentioned they are not direct comparisons (same car, multiple tire tires switched on consecutively, a la tirerack). To the powers-that-be on the site - such a test would be an EXTREMELY useful article, and likely increase your site hit count dramatically as it would be cited all over the web. No doubt it would difficult to perform though...