Just noticed a Sky News interview with the Met Police Commissioner going on the BBC News channel. What's the agreement between the broadcasters in events like this? Is it a matter of the BBC and Sky having a mutual agreement where say, if you give us this - we'll give you that? If so, how do they go about distributing the VT between one another?
It's a 'pooled' interview, a very very common thing. The person - often a politician or other senior public figure - agrees to do one interview to be provided on a 'pool' basis. It is then made available to all the broadcasters in the U.K. pool (BBC, ITN, Sky) at the same time- no exclusive first showing for the broadcaster that filmed it. If the broadcasters all have trucks in a pariticular location they might link into whoever is playing out the pool interview so they can record it / feed it back but what usually happens it that it'll be fed back (file transfered or played out) by the broadcaster who recorded the interview. The other broadcasters book circuits to that broadcaster once a playout time has been agreed. (They wouldn't downlink another broadcasters satellite feed in all but the most extreme of circumstances.) This feed may be arranged some time in advance, other times it's arranged with a matter of minutes notice. If the other broadcasters want to broadcast that interview / feed as it's coming in to them they are allowed to.
Who is the pool tends to rotate around, but it's not a strict rule. It may come down to who has the crew / facilities in the right place at the right time. The pool for royal stories (most of which are known about in advance) tends to just come down to whose 'turn' it happens to be. (Although in the case of the royals there is a cameraman who is paid for by the BBC, ITN and Sky who films most royal events.)
For larger events the pool may be a camera provided by each broadcaster that is then mixed by one of them. If it's an event occurring in several different places (like the Queen's jubilee) one broadcaster may be the pool for one place, another for the next one and so on.
Whilst UK broadcasters are competitive on an editorial level on a technical level they're good at co-operating when needed. So sometimes arrangements for a pool are adapted by the people on the ground for one reason or another.