Got around to watching it today and after I was done, I was checking out the features and it has a mode called "Surveillance Window" which you can activate. Once you do so the movie is restarted and from what I know of IME, thats the kind of feature this is. It has audio commentary playing, then at certain points it will go into behind the scenes featurettes explaining how things were done (the one I watched showed how they did the ferry explosion scene).

It was all completely seamless and i'm wondering if BD-J was used for this or was it something like Lion's Gate has done where they put a full second encode of the movie on the same disc, but with the added featurettes?

Sounds more like seamless branching, I think BD-J would be more 'dynamic' for lack of a better word.

I watched that movie and that feature....it's nothing compared to actual IME

I also was wondering if it was 2 encodes or seamless. If it was 2 encodes could that be why they only used a 16 bit PCM track instead of 24?

I'm betting it was a double encode. The DVD has the exact same feature according to HDD, and that sure don't support BD-J 1.1.