Google has always allowed anyone to bid on trademark keywords, you just cannot use trademarks in your ad copy, which violates IP and fair competition laws. Unless the big companies had a backdoor deal with Google until now, this is the way it has always been, as I have been able to bid on trademarks and people can bid on my trademarks. When I file for infringement on my trademarks with Google it keeps people from using them in their ad copy, but not bidding on the keyword itself.

For instance, Audi can bid on BWM, so long as their ad title and copy never has "BMW" in it. But if they said "Do you like BWM’s? You’ll like this better!" then that would not be allowed and is enforceable.