Hopeful! If ever there was a 'commercially sensitive' arrangement, it would be that between ITV Studios and BBC Studioworks.
Two things, about your question, though
1) Are ITV paying the BBC for useage, lock, stock and lighting grid for year round residency of TC2 and TC3 as a whole self contained deal - or are they paying the rent on the use per sq foot/mtr on the floorspace of the standing sets in TC's 2 &3?
2) You'd think, that this deal renting out two studios is a heck of a lot cheaper in the long run, than finding a empty or existing space to convert central London location and building, and fitting out 2 or 3 broadcast spec studios in it.
I think the actions of ITV answer your question here - ITV would not have entered a sublet deal with BBC Studioworks if it were not financially suitable for them.
As ITV have no intention of leaving Television Centre, it seems it must be cost effective for them to continue with the sublet deal with BBC Studioworks.
The original discussion was that ITV Daytime would move back into three smaller studios on the Southbank site in around 5 years time, so building and kitting out three studios and providing the services needed to run the productions there must have been financially poor for ITV, and so remaining at Television Centre is the best option.