Very cool. They apparently have been doing that unofficially for a little while.
I took my 2012 Retina Macbook Pro there in December 2014, because it was saying "Service Battery". After they ran the diagnostics the message was gone and they said it was ok, but the Battery capacity was at 82%. They said they usually replace it if under 80% but they offered to replace it if I wanted to.
The tech support guy then checked my AppleCare status and noticed I was covered until June 2015. Then he suggested I'd rock it for a few more months and come back closer to the expiration of the AppleCare contract. Sure enough, in May the battery capacity was at 75%, I took it there and they replaced the battery, no questions asked.
As a bonus, the space bar was acting out a bit too and they said that since the battery is somehow connected to the top case, they replaced the whole thing. Now it feels like new.