It depends on the service if things move gracefully or not. The incident explains it's only EC2 (and dependent services) in that AZ, so if they try to route traffic for services hosted on EC2 to that AZ it's not working (and customers running instances in that AZ have lost access).

The other ones are not impacted. They always like to tell you to pay for more than one instance in different AZs so if this happens you don't get impacted.

I doubt that there is enough capacity to evict a full AV to another one.