BT Broadband users have free access to the three channels in SD
BT Infinity users have access (subject to payment of a £3 per month fee, waived for the first year, if ordered before 1st Aug) to the channels in HD,
They've kept that one quiet.
So what do you want to do, if you are a BT Broadband customer, so have access to 'free' BT Sport 1&2 + ESPN, and want to watch them in HD via Sky?
It doesn't seem very clever, buying transponder space and running 3 channels in SD for non-infinty customers, when (I'm guessing) the majority of viewers, are also paying for the Sky Sports Channels and can see those in HD.
Gun, Foot, Bang, Ouch from BT there...
"Peel me an Onion, I'll be back for Breakfast.."