[DTV]

In other words on a normal Sunday us the newsreader tied to a specific timescale to opt out at 1506 etc and fit in the shirt bulletin with the rest if the hour on automation?

I'm not sure how automated the presentation process is these days, but all BBC World News bulletins are limited to a certain runtime (e.g., a typical bulletin is expected to end at exactly xx:26) for breaks etc. During certain breaking news situations there are obviously exceptions to this, but World programming cannot overrun in the same way that the BBC News channel often does - it is more clockwork and the channel has more timing points that have to be hit dead on (unlike the NC which only has to hit the TOTH* (and even then sometimes doesn't)). This is why you often get rushed goodbyes at the end of a World programme.

(* I recall somebody on the blue place once jokingly suggesting that the definition of a slow news day was when the News channel's quarter-to headlines actually took place at xx:45)