[Stooky Bill]

If its the same sort of thing Red Bee provide for the BBC it's not a 'hot spare' or a 'DR' but a dual site setup.

It's still not 100% resiliant, nothing is. There's still potential for things to go wrong, for example there had to be a system to switch between sites. Also having two sites enables you to do maintenance on one while the other runs by itself. What if site A is having work done and site B has a failure?

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Thing is that it's sometimes not possible to instantly put up a breakdown caption. Sometimes when things go wrong it doesn't matter how many people are present if the technology's against you. 

Also in events like this there's a certain amount of reaction time and even longer time to assess what is going on

As for a lack of announcer, the audio during  breakdown slide was totally corrupt so I think even if there was one he/she would have had trouble talking on air

I get that sometimes there will be a catastrophic failure, but isn't there usually an emergency cut or router cut to get a dedicated source with the apology caption on air quickly even if the rest of the suite has died?

Depends how it's been designed. With new systems like playout there's usually always one scenario or set of circumstances that wasn't foreseen. But when that does arise lessons are learnt and change are made either to the software, hardware or working practises 

Also of course there's some circumstances where having an emergency cut or similar isn't going to be the answer, if power was lost to the suite or even worse the whole building. Yes of course things are backed up with UPS or dual supplies but it does happen