You heard the part about them being OFF DUTY, right?
That would tend to imply that there were people ON DUTY.
They can go for the ambulance all they want, but it's not going to be there.
I work in a town with ON DUTY crews. If I'm OFF-DUTY, and a call goes out, why am I going to go to the ambulance? That's what the ON DUTY people are for. If it's a bad-sounding pediatric call, and I'm closer to the scene than the ambulance anyway, guess what? I'm going to the scene (sans any sort of warning device or sticker). In a choice between the scorn of EMTCity and possibly doing some good in a critical situation, the patient wins.
Granted, wouldn't happen since I don't live anywhere near the town, but you get the theory involved. I hope.