Here at Tire Rack we have the opportunity as sales specialists to test most of the tires that we sell. We have over the years used a wide variety of vehicles: BMW 328i, BMW 330i, Lexus IS300, Jeep Grand Cherokee, Porsche Cayenne. And we have used several different configurations of our test track, even testing tires on an ice rink.
However, tests aren't meant to be compared one to the another as illustrated in this Club Lexus forum post.
While we are consistent in how we display the information, it's not recommended to try and compare the results of different tests. The ambient temperatures, road conditions, vehicle conditions, sizes, etc. could all be different. You can compare results within a test and take into consideration results from other tests when deciding which tire to buy.
Tire Test Results