The question is portability, but what I think you mean is out of network coverage.
Yes... I did mean out of network. My understanding of what happened, is that our HMO doctor received "bonus" dollars on his patients for keeping their healthcare costs under certain limits, and that authorizing the Florida operation, and subsequent care, would have cost him $$$. In fact, when the surgeon who operated called him directly to authorize the operation, he refused to take the call. We finally settled the issue after meetings with the arbitration board, but there were many anxious moments.
In any case, after encountering the situation, we signed up for Angelflight, just in case a similar situation recurred. Don't know the current cost for air ambulance, but at the time, it was over $20,000, and we figured the signing on was worth it.
I'd say, something to consider for travelers who don't want to get stranded far from home in case of a medical emergency.