Is UnitedHealthCare kidding? As one who has bounced through that outfit and then moved on to Aetna before it became a burdensome nuisance, I can report from personal experience that I often wondered whether the Aetna enforcers ever read their mail. A full eight or nine months after we switched to our current insurer, I and my wife were still getting notices from it despite a number of phone calls and letters to it with reminders to Aetna that we were no longer under its so-called tent.
In the New York case, the hospitals might be pleasantly surprised if they ignored the threat. It's possible that UnitedHealthCare would not catch up with such defiance for many months. What would you lose that you might lose anyway?