Well, I have StarzHD on my cable system. Many of the movies they have are frequently NOT shown in HD. I'd say it's 50/50 chance.. Would be interesting to see if VOOM ends up the same way. (In the movies description on Adelphia, it says HDTV otherwise it's shown in SD narrowscreen...)
For example, right now (2/9 at 9:15pm) the movie on StarzHD "the shipping news" is not HD.