I got it from here:
Originally Posted by Sean Whitmore
And for those fans who have been trying to fit current continuity in with stories that happened prior to "Infinite Crisis" Kurt [Busiek] has this to say...
"Like the post-Crisis era, the new era that follows INFINITE CRISIS is a new era. As such, it isn't trying to fit snugly into the facts of the previous era. To use the 'house of cards' metaphor again, it isn't a matter of taking out a bunch of cards and slipping in another bunch, but preserving the same basic structure. In the wake of a continuity-revamping crisis, what you have is a new house. A brand new structure, not the old one with cards missing. It may have features that look like the old house, and features that don't, but that doesn't mean it's the old house with a facelift. It's a new house. It's full of some things familiar, some things unfamiliar, some things changed, some things new. And now we get to explore it and see what's there. You don't need to know everything that's in there going in. You didn't the first time you picked up a comic, after all. You can explore and learn and discover. It does mean that, yes, all that stuff you knew about the old era is now outdated information -- still true of the old era, and a valuable part of it in the "Man of Steel" trade paperbacks and all those back issues on my reference shelf -- but not something that necessarily fits into the new one."
So, while the DC Universe Post-IC might look like a continuation of the Post-Crisis era, it's not. It's a totally new continuity where things look similar but are different.