An OC-12 is the minimum practical level being able to support 3-6k subscribers simultaneously with their SD levels of resolution. (You're actually probably going to need an OC-48 or an OC-192 to do it right- an OC-12 is overselling things pretty badly actually...)
Expense of an OC-12 setup is $100-300K for stable hardware and the link.
Ongoing expenses will be something on the order of 2k/month.
That's COST. Regardless of it being the ISP doing it. And the big-boys are bitching about bandwidth hungry stuff already and wanting to charge everyone more for it, users and providers alike.
This is DRM snake oil that's being peddled to investors and the publishers. The expenses of doing this the right way so that it'd work is astronomical. Bandwidth and the latency that comes from not having enough thereof will kill this idea deader than a doornail.