They start filming at 21:00.
When they say they are going to an ad break, they continue filming while we watch the ads.
Therefore after the first ads, there is a 3/4minute delay which grows with each ad break.
So basically it starts off completely live, (give/take 1 or 2 mins) but is delayed a fair bit by the end.
This is true of BB10 because I can see the studios from my window & I see all the lights go on, and the fireworks in the finals etc.
