I don't know if the Mod fix's it, but whenever I call 911 and request and ambulance, it comes flying in like a bat out of hell, sometimes killing a driver in his car or a few people on the sidewalk, and even once flipped a Police car I had called to stop this one guy from shooting me. (I do this, enrage a gang member, point a gun at him, he wants to fight, let the cops do it) But anyway, after the ambulance causes enough rampage and distruction, Niko feels Jelous and 3 more ambulances are on the way, he simply gets out and says "Who's hurt?" (Even once while standing over the body of a wounded Police Officer begging for help) then he'll just stay there awhile, and leave.
Wtf?
But the regular, responds on random, will heal one or two guys.