Well teletext, in it's broadest sense, was used to distribute the channel 4 'live' schedule to the various ITV companies when C4 passed through their premises, the system was called 'Ident'. And GMTV used 'talkback in teletext' or 'tit' as it was commonly referred to, to distribute the production gallery talkback to the various places that insert the local news opt outs. Neither were receivable at viewers homes.
Ident was used by BBC World to trigger ads and other opt outs by the various facilities around the world that distributed the channel.
There were 2 pages - one for ads and one for programmes and triggers for readying VT
machines and cutting them to air (the problem was that if they readied 'stood up' the VT machine and then the break was delayed then the tape didn't start as accurately as it should do and it could look a bit messy)
These were blocked from going to air, at least in Europe where it was replaced by the channels teletext service (that in turn generated the break filler, but that's another story)