Interesting additional comment from seenit.com:
BT will be pleased to have secured access to the channels before YouView is fully able to support Sky’s NOW TV streaming service which offers access to its sports, entertainment and movie channels on flexible, monthly terms.
Although the service is currently limited to offering a movies on demand service, a future update to the YouView system will add support for its live channels, allowing Sky to retail its sports and other channels direct to BT TV users, just as BT retails its sport channels direct to Sky’s subscribers.
http://www.seenit.co.uk/bt-wins-right-to-sell-sky-sports-1-2-to-youview-users/
The YouView update has just happened, and Sky are understood to be busily rewriting their YouView NowTV app to run the live channels, so presumably BT TV YouView users will soon be able to get Sky Sports that way. Though that will be unicast, so unlikely to tempt BT Vision box users away from the multicast version, I would think.