I seriously doubt they would rank one of you highly and not rank the other highly simply because you come from the same medical school. I mean, if I put myself in a PD's shoes, I would want to rank everyone in the order that I would want them to be in my program and would not feel compelled to 'choose between' two candidates just because they completed medical school at the same institution. I suppose I would have to 'choose between' them in the sense that the system obligates me to rank one higher than the other; but, I would feel free to make both of them 'ranked to match' if that's where their candidacies naturally placed them.