The owner's son of Cablevision (Jim Dolan) has some kind of spat with Mark Cuban. So the possibility of Voom every getting HDNet is questionable. The Dolans/Cablevision own the Knicks, Rangers & MSG (Madison Squar Garden) as well as MSG Network, Fox Sports NY and has a 50% partnership in Fox Sports Net overall.
Mark Cuban owns the Dallas Mavericks and HDNet. As you can see besides the personal issues there are business issues here. Dolan may also be interested in keeping eyeballs off the Mavericks even though it may not affect you.
Don't be surprised this is just the way Cablevision operates. On their cable systems they never offered TCM because they own AMC. They never offered MTV2 because they owned MuchMusic (Now called Fuse). There are a bunch of other channels that are hard to remember now. But until satellite competition became real fierce; they eventually had to offer these channels.
HDNet I suspect will not come until it becomes ubiquitous and not having it becomes a competitive DIS-advantage.
But don't look for it any time soon.