More likely there is no comment until the UK government makes the announcement public - rather than responding to 'informed sources'.
BBC is caught between a rock and hard place. Its journalists 'need' to report the story or risk being accused of 'censorship' for not reporting on the rumour/leak/background-briefings when other news organisations are reporting those, but at the same time the BBC board [0] (10 non-execs and 4 execs) will presumably have been preparing a measured response to publish once the UK government makes the 'official' announcement.