It has been years since I watched the DVD, but if I recall correctly this was not really a proper extended cut in the traditional sense, it was just the theatrical cut but if you played it in the enhanced mode an icon would occasionally appear wherever one of the deleted scenes would have appeared in the film, and by clicking on it the film would stop and you would see the deleted scene in it’s raw un-finalized form. They were not integrated into the film proper, there would just be icon links that allowed you to watch the deleted scenes in order while you watched the film.
I also remember hearing around the time X2 was being released that there were plans at one point to film newly shot footage during the production of the sequel that would be integrated into the first film to create a true extended cut which is what X-Men 1,5 was supposed to be, but for whatever reason that idea fell through.
EDIT: Upon looking at the Blu-ray features (which I have never watched), The Enhanced Viewing mode that is offered on that disc appears to be exactly what was on the DVD. There was never a proper extended cut on any release as far as I am aware of but I would love to see someone put one together.
