I realize Glenn said he would not comment further about this, but it seems to me that he may have ben trying for Heaven & Hell and Mob Rules era Black Sabbath. That sounds like something Glenn would try to pull off as opposed to Dio who tours the states almost annually.
I could be way off on this but that sounds a hell of a lot more interesting than Dio by himself. Besides you'd think Tony Iommi and Geezer Butler might be more interested in doing this than the same ten songs or so on Ozzfest every year.
I don't know, just an idea.