Been there - almost
Last year, I was involved with a disaster; not on the IT side though. Some of my thoughts.
If you think that the authorities have planned for BC / DR, think again. Most of them will have had numerous meetings and discussions, but none of this will be in the slightest bit relevant when it all goes belly up. Most of their staff will not have read any plans and will mostly stay in offices hiding; those that go out to meet the public will stand around looking bewildered.
This includes Police, who will possibly have some junior staff standing around being visible to "prevent civil unrest / looting" but actually achieve very little. They will probably have a silver & gold command structure, which will prove to be as useful as the proverbial chocolate tea pot. They won't talk to fire or ambulance service, so expect fire engines and ambulances to end up in the wrong places.
The army do sometimes get called out, but they are very few in number these days. Being cynical, I might suggest that they'll be around whilst TV cameras are there, so that the general public can be assured that "something is being done"; but as soon as the cameras get switched off, the army will be on their way back to barracks.
Communication seems to be a bad word; none of the organisations that should be talking to one another or to the public will actually have a clue how to get information out. If any government agencies are involved, they will actually make matters worse by passing incorrect / out of date / irrelevant / misleading information to the media.
National news media will cover the story as long as there are potentially "serious consequences". After that, you're yesterdays news. Local media tend to do a better job of getting their facts right and of keeping on top of the story.
In the end, more will get done by volunteers, or by individuals helping themselves out.
Afterwards, all of the relevant public bodies will tell everyone what a great job they did; and senior people will receive awards for their contributions. But at the same time, they will all bemoan the fact that they don't get enough funding and will spend more time in the press telling everyone of this than they did during the disaster in providing information that was relevant to the people affected.