Ady posted some info over on the facebook page I haven’t seen mentioned here:
i’m using the 6.1 DTS-HD tracks as a basis for the audio, but it will be a new mix due to all the extra elements and edits. The rear centre channel is probably the lamest channel i have ever heard in a 6.1 mix. there are only about 4 times thought the whole movie that any effects come out of the channel and that is only a split second effect. Plus the rear left/right channels are pretty lame too, with really hard music edit cuts that just suddenly come in, or ambient effects that just suddenly stop for no reason. This mix is going to be ultra surround sound. Due to the nature of this edit there is no way i can use the theatrical PCM tracks
The blu-ray version will be a BD-25. The sound mix will be a DTS-HD 6.1 mix on the blu-ray and a AC3 5.1 mix on the DVDs. When i say “ultra surround” i mean a mix that actually utilises all 7 speakers instead of just some music and sound effects now and then.
This is from 2012 it might have some updates since then.