It seems to me that if you're being evacuated from some disaster situation, that your plane won't be landing at an airport in ANOTHER disaster area. So my BOB for that scenario would be cash, credit cards, a deck of cards, and a book. Pretty much what I carry on a plane every time I get on one. You would probably want to take some personal documents too if the evacuation might turn out to be long duration.
If you're planning on the plane landing in a war zone or crashing in some remote wilderness area or ditching into the sea then things would be different. But most likely you'll be evacuated to some civilized and safe place without incident. And you'd probably be evacuated to some nearby place with climate similar to what you're used to. They're not going to fly you from the Caymans to the Arctic. The clothes on your back would probably suffice, if you carry money to buy more when you arrive at your destination.