I tried to play the "drive any car" free weekend. I clicked on the GT3 Mustang (which i do not have in my inventory) and it took me to the store and "free trial" on Raceroom Raceway. Just like any other car trial - so nothing special. How was it supposed to work? Or was that it? If so, that was sorta disappointing.
Basically you could go to ie. single player and choose everything. So a full race on a track you don't own with a car you don't own.