It sounds like this is another manifestation of the problem BA have made for themselves by cutting costs and relying heavily on sub-contractors and electronic check-in.

I had a similar problem last July in CDG, though I can't find the thread as the stupid search isn't working at present. The gist of my problem is I got to the self-check in machine in Paris which gave me a spurious error message. The dozy machine minding sub-contractor eventually figured out the flight was cancelled and I stood for over 2 hours on a hard floor while 2 people tried to re-book an A319's worth of people - a process that took so long I'm certain I missed one possible alternative flight. Ironically that was the flight that got me my Silver badge, though I very nearly turned my back on BA.

It seems to me that if BA feels it has to go down this electronic / sub-contractor path to save money it exposes itself when it hits a problem like a cancelled flight in a remote location, because it doesn't have enough staff to provide the resilience to get people moving again with the minimum delay. I frankly can't see any reason why the check-in kiosks can't by default offer the next available flight, but also function like browsers to offer the same features as ba.com so the passenger can re-book himself and avoid insane waits. I know this won't cover every eventuality, but if it clears 70 or 80% of the simple cases you can use the people to take care of the other.

Come on BA - if you want to use technology to save mney, then invest in it properly.