"As well as access to BT's library of on-demand content, users will also be able to watch hundreds of movies and other digital content, including its near-live FA premier League football matches. ... "The reason for streaming only on the Xbox is because currently the console does not have the capability for live TV or enough hard drive for practical downloading of content," explained a BT spokesman."
http://kotaku.com/343026/set+top-xbox-not-able-to-receive-or-record-live-tv
Bummer, no PVR functions...and it's UK only no?