If my suspicions are correct, I run in the same area as CaptBP. Last time I checked, there are very few MVC's that are dispatched as confirmed injuries. Most times, they are refusals, or if they are transported, they are transported to the local hospital, which is not a trauma center.
On the original point, in our area, we usually advise dispatch of the second accident and check to see if there are any injuries. If there are, we stay and the rest of the MVA assignment is dispatched and another ambulance is dispatched for the first call.