I remember going to the DVD/BluRay panel at SDCC 2012 and the guy from Warner Bros. said that this 3D restoration was going to involve roughly the equivalent of six movie restorations due to the type of film that was used and how the 3D was shot.  Basically since the film was in color, they shot it on three strips of film, red, green and blue. Since it was 3D, they were using two cameras, so they're cleaning up six strips of film to bring us a colorized 3D version. Wow.