[i.h]

developer.apple.com  - ignore the references to IOS. Besides, It's the routers (hops) along the way that facilitate multicast. with the internet Group Management Protocol (IGMP), along with class D IP addresses. Multicast is actually used a lot more than you think it is.

Besides EE have worked with apple to launch a bespoke solution. It's not impossible run a YouView box inside a virtual machine and have it running in a Apple TV app container.

I don't think you can safely presume what I know or think.

There's a substantial difference between how it is used within the local network, for device discovery (ie what Apple's really talking about in that developer article), and how it is used for IPTV, especially where wifi is involved and you can't use that to efficiently transfer large amounts of data in a multicast fashion (it will try to do so at a very low data rate). I will reiterate that BT seemed to have trouble getting it to work with their own set top box, as it required a later firmware update to enable wifi functionality.

I'm not aware of any other IPTV provider using multicast on the Apple TV - indeed Swisscom explicitly mentions that they had to go unicast

www.v-net.tv 

The second notable device and distribution innovation at Swisscom is the recent introduction of Apple TV devices as a second set-top box option shipped by Swisscom for on-network Swisscom customers (in a Swisscom home). These now sit alongside the ‘original’ Swisscom-developed STB platform that harnesses Android Open Source Project. This also turns Swisscom Pay TV into an app experience and delivers content as unicast ABR, rather than the classic multicast IPTV delivery into the classic Swisscom-developed STBs.

All content, including the approx. 15 UHD linear channels from Swisscom, are served as unicast ABR streams through the Apple TV set-tops – which becomes the first unicast STB deployed by Swisscom. Asked about the trajectory towards all-ABR television, Schmidt pointed out that everyone knows the world is moving to all ‘OTT’ whether in the near or far future.
“There is a lot of innovation in this direction, so we will be driven in this direction. Companies will need core networks that are ready for unicast [as the default TV delivery].”