my interview was open file too. i'm pretty sure all of them are at least to some degree, because part of the interview day is a file review where you go over your application with an admissions counselor and explain any low grades, make sure you have all the pre-requisites, etc.
in my actual interview my interviewer didn't actually open my file per se, but she had obviously read my application because she refered to some of what I wrote in my essay when we were talking.