I think it depends on what is considered to be an emergency. Hospitals only have to stabilize a person and then they can be transferred to a public hospital (or a hospital that particpates in reciprocal services with the county or city) for further treatment. Private hospitals do it all the time and in some cases investigations are done:

http://www.lasvegassun.com/sunbin/stories/lv-gov/2005/jan/12/518114948.html

Surprisingly, you seldom see illegal aliens transferred which I do not understand. The federal government reimburses all hospitals (public and private) for treating illegal immigrants while the federal government does not reimburse a hospital for treating a U.S. citizen (such as myself). While medical quality of service is outstanding in the U.S. the cost of it needs major reconstruction. I think more and more people are considering supporting the Democrats in their quest for socialized medicine. I'm curious as to how many people if any have relocated to Vermont since that state started providing medical care to all residents.