My understanding is that they can see where you've been accepted if you've paid the deposit fee at that school. Someone please correct me if I'm wrong.
BTW- I was rolling my eyes, because, in my opinion, saying where else you have applied / been accepted often does have an impact on their decision. I'm sure there are plenty others who agree with me.
Just because they are not 'supposed' to ask you where else you have interviewed at/been accepted, does not mean thats the way it happens in the real world. I have been asked 'where else have you applied/interviewed at' in 4/5 medical school interviews I have experienced. This is why I threw in a sarcastic smiley.