The case is how old?
I'm sure there are still major issues in HEMS in the states, but you asked if this alerting practice is common!? Maybe it's the exception that proves the rule, but I doubt it:
I was told that here in eastern Pennsylvania/northern New Jersey the first and second responders are clearly negotiated between the operators. Only if the helicopter responsible for a certain area is on a call or grounded another company will cover.
I stand to be corrected.