In my city, the ambulance service is run by a private contractor, but the city government offers ambulance insurance to residents. It's included on my monthly water/sewer/trash bill and costs about four dollars a month. All ambulance services are free. A friend has taken two ambulance rides over the past few years, with nothing out of pocket for either of them.

The insurance is optional. If you don't want to pay the four dollars each month, you don't have to, but it's so cheap and easy why wouldn't you for the peace of mind it offers.