"something to which answering questions from customers does not usually contribute."
Except in the sense that ignoring customers when you're company has f**ked up is a good way to ensure they stop wanting to be your customers.
And if enough of them do so with your business then pretty soon you're not going to be needed anymore.
Keeping customers (internal or external) informed should be part of any generic "S**t-hits-the-fan" DR plan. IT should not have to do it but there should be some kind of SITREP process that can be used to inform customers and someone on both ends of it who deals with it.
Let's be real. S**t will hit the fan. Anyone who's thinking "That never happens to us" is deluding themselves. It has simply never happened to you yet. So fail to plan or plan to fail.