From Bleeding Cool:

Action Comics- The only other title (along with Justice League) that will start out in the past. The first arc will detail Superman’s public debut. At this point, Dan Didio went on a tangent to explain that DC wanted to let go of the past and move forward. Any changes in continuity would be addressed in-story as needed, but that they really didn’t want to get bogged down so these reveals would be gradual and as they make sense in the story. There is a document in the DC offices that fleshes out exactly what has and hasn’t happened in the New 52 Universe. As an example, the Death of Superman storyline has occurred. See Batgirl below for another example.

Yep, sounds like they know what they're doing. Just don't wanna tell us.