Local isn't a good measure here, though. The BBC local stream is literally just going to be posts by BBC employees.
The global stream isn't a great measure, either, frankly, as journalists primarily want to yet their posts seen, not see a huge field of noise. Those who are doing digging for social media stories maybe want a wider cut of things, but they can still do that through their replies, and through global. Search just isn't going to be as effective as on generalist servers.
But then, search isn't super effective on Mastodon, anyway, and all the big generalist servers are running Mastodon.
There's nothing preventing them from using secondary accounts on .social for research, though.