Yes but how are current bt vision customers going to react if they are thrown off sky sports in August purely because they live in areas not yet covered by infinity / multicast?
I think that's not going to happen as I'm sure there will be a fairly long transistion phase. However, if it did this it could end up in the situation that some of its customers will be able to get SkySports but not BT Sport. Perhaps it can get temporary DTT capacity for its own channels, certainly ESPN 34 could be free.
Those who predict BT will switch off DTT broadcasting quickly on cost grounds need to consider that these DTT channels cost £10m each per year - relatively insignificant against the investment in sports rights to date which are creeping up towards the £bn mark.