Phone calls are definitely not allowed. Emergency or no, it should have been taken in the vestibule.
I was in a quiet coach recently when a lady across the aisle from me took a Facetime call on her iPhone. She did use headphones, and she spoke quite quietly (probably helped by the microphone built in to the headphone lead) and the call didn't last all that long. So I waited politely until she'd finished the call before pointing out to her the fairly prominent notice on the window over the table at which she was sat, which explained how passengers in the quiet coach are supposed to behave. To be fair, she was quite apologetic about it, and did go into the vestibule to make another call later in the journey. But to counter that relatively benign incident, I have experienced far more egregious abuse of the quiet coach by mobile users.
I sometimes think that some folks simply don't realise that they
are in the quiet coach. I'm not sure what the answer is, without making the signage uncomfortably obtrusive. "QUIET" woven into the upholstery, perhaps? Invisible when the seat is occupied. Large signs on the coach and vestibule doors? Wouldn't be seen when a lot of people are getting on at once. Most quiet coach users do seem to have seat reservations, and the quiet coach does usually seem to get booked up more quickly than the rest of train, so one would
assume that it's a conscious choice to sit there. So why choose the quiet coach, and then fail to keep your noise down? Or do they expect it just to be everyone
else who has to be quiet? It baffles me.
I actually find the worst people to share a quiet coach with are groups who engage in animated conversation around a table. Far too many people seem to be unable to have a conversation at a civilised volume when seated across a table from each other - and when four people are involved there's always a tendency for the volume to ramp up. When the other 80% of the people in the coach are being quiet, it makes involuntary eavesdropping almost unavoidable. Noise-cancelling headphones can help a bit - but why should one have to use them to get a bit of peace and quiet
in the quiet coach? I think there is actually a case for making quiet coaches all airline seating, to reduce the tendency for this kind of behaviour.