BT in the UK do this. It's awesome, but doesn't fix encoding delays like iPlayer is suffering from. Plus, it's over their Network which is a subset of the UK public internet infrastructure.
I had an old blog page about how it was designed but I took it down. May be worth revisiting it. That said the general public prefer unicast so they can watch it when they want, which renders multicast a moot point.
Nagra sell a system that does it to ISPs around the world and have done for at least 10 years. I'd been hoping we'd see more of that in the UK, but there has been virtually zero movement probably largely because of our patchy broadband service. I'm assuming the Sky Q boxes are heading in that direction eventually.
I had an old blog page about how it was designed but I took it down. May be worth revisiting it. That said the general public prefer unicast so they can watch it when they want, which renders multicast a moot point.