No matter how you feel about BBC ( I would at least posit that they are significantly better than some of the corporate, for-profit news networks out of America), journalism and professional-quality media is important to informing people and providing the very first thread of accountability in democratic society. On top of that, I think that self-hosting fediverse software on an official domain (like "social.bbc") is the ultimate form of content verification, and it much more effective and egalitarian than awarding "influencers" with blue checkmarks or whatever.
Overall I see almost no downside to the BBC hosting content on the Fediverse, and I hope that other media organizations follow their lead on this one.