It can be treated. I've seen worse. If the dog has an owner, the vet can treat it. Dog's have flexible skin that can be pulled to stitch it up after it's treated. If the dog is still seen running around with that open wound, then it's chances of surviving is high if taken to the vet soon.

Well, sadly, there are not many people that will not bother to catch a stray dog for the sake of treating it and adopting it out or keeping it. Maybe if it were a puppy, but a full grown dog? Highly unlikely. I guess the best thing to do is to call SPCA, they'll probably put the poor thing to sleep right after catching it.