Yes, that's exactly how it was done.
The breakfiller consisted of 30 second sections with the graphic 'news', 'sport', 'business' etc and these were on the disc in various lengths in different combinations. The breaks were in the automation schedule as a 3 minute, 2 minute etc. That triggered the breakfiller system to start and or did everything automatically.
The text was taken from BBC World's teletext service which was done by Intelfax but had news, weather, sport content (I think it was the same as seen on Ceefax but not UK orientated). It was put on live as the breakfiller went out. It knew what order the subject matters were so put business news on the business background etc.
If the breakfiller system wasn't working, which wasn't uncommon apparently, there was a backup which was a tape with generic promo text on it instead of news stories (like this: https://youtu.be/Sjnoiiha_H4?t=252
Of course the idea was for no one to see the filler as all their partners should have sold advertising in those gaps. The idea was that if the ads were 30 seconds long then if the break wasn't filled then the ads would finish neatly between the sections on the breakfiller. I remember seeing World in Asia on holiday and the timing wasn't bad mostly. These were triggered on the VBI by a system called Ident which also provided a teletext page style display showing when the next breaks were due. There was also a cue dot should that fail.
As mentioned it was replaced in 2001. Partly because the discs were difficult to get - news used them for their titles at the time and also struggled for blanks. But also because World's teletext was ending.
Last edited by Inspector Sands on 1 November 2018 9:27am - 4 times in total