How does that handover work? Are both studios fed to Chiswick on separate circuits and they cut at the agreed time, or is there some kind of switch at TV Centre?
Certainly sounds like it's not a soft opt situation where TC3 cuts up TC2.
I would expect that TC2 and TC3 are routed separately to ITV's playout areas.
It would, of course, be possible for TC3 to cut to TC2 (with ITV playout staying on TC3's circuits) for the handover until the first commercial break (to keep it tight and allow a bit more of a finessed sound junction), and then ITV could switch to TC2's circuits direct after the first break. Whichever way round it is - I'd expect the cut to be on a hard count not a 'whenever the person has finished talking' junction.
Steve in Pudsey gave kudos