It's similar to what happens with BBC Radio 4 late at night (and into the early hours of the morning), with domestic programming coming to an end for the day but with the transmitters then carrying BBC World Service programmes until Radio 4 comes back on air later on.
Although the BBC News channel doesn't completely end its own output late at night, it does start to incorporate some programming from BBC World News (which is the TV side of BBC World Service), with Newsday being a BBC World News programme targeted in part at the Asian business community.
https://en.wikipedia.org/wiki/Newsday_(TV_programme)