I'm confused. I sometimes check the Playstation Blog EU to know what's new on the PSN Store Europe instead of actually turning on my PS3 and logging on.
Now it looks like XCOM might be free, judging from the picture at this link:
http://blog.eu.playstation.com/2013/07/03/playstation-store-update-gt6-demo-new-ps-plus-games-more/
But I can't see it actually outright stated in any of the updates that XCOM became one of the games in the Instant Game Collection.