Yeah I royally fudged up that wording. I meant aside from the dedicated news studios, it was BBC News & Current Affairs' go-to "TC" studio.
Yes - I think TC2, then TC7 afterwards, was the 'bought out' small studio used by BBC News. They would only use other studios if TC2/7 was out of action for some reason, as they had already paid for their existing 'main block' studio.
The same approach was used by BBC Sport in TC5, when that was their bought out studio.
For a relatively long-time all the small studios at TV Centre were bought out: TC2 for CBBC, TC5 for Sport, TC7 for News.
As they were much smaller than TC3,4,6 and 8 - the 'Medium sized' studios at TV Centre (which were the popular studios) - the smaller studios were harder to sell for ad hoc shows, and selling them as a buy-out made more commercial sense.