As I've mentioned on several different occasions, it's a huge mistake to wait until a tragedy occurs to explain the truth about response times to your community.
Response times should be measured from the patient's perspective. In other words, from the moment the dispatcher picks up the phone and says, "9-1-1 what is your emergency?" to the moment a professional rescuer arrives at the patient's side.
There is no excuse for allowing our real response times to be ambiguous. It doesn't matter if some other organization does the dispatching. It's the EMS system’s responsibility to figure it out because we are ultimately responsible for the community's chain-of-survival.
In other words, if our chain-of-survival is broken (and it surely is if we have no idea how long call processing takes) then it's our responsibility to educate our citizens and our elected officials of that fact.
Remember, millions (perhaps tens or even hundreds of millions) of dollars in 9-1-1 taxes are collected each year in the United States. Where does the money go? Our inability (or unwillingness) to measure "9-1-1 call received" to "patient's side" is completely unacceptable and patients die because we pretend that our response times are better than they actually are.
Where's the accountability?
We must never allow ourselves to become acclaimated to things that would outrage members of the general pulbic once the facts become known.
Explaining why EMS wasn't there "in 4 minutes" to treat a child in cardiac arrest is not a particulary good backdrop to have this conversation with the taxpayers.