First a disclaimer: Yes, I am a program director from a certified program, but I will speak in generalities about a system that is anything but standardized.
I have been watching this forum since it started. Just wanted to let you know the truth about call backs. They serve several functions but in general are frowned upon by the AAMC and all concerned parties. They are by no means illegal, unless you tell the applicant where you rank them or ask specifically where you rank us.
I do not know how UPITT works but I can guarantee that Dr. FU is not calling every interviewee. It is probably good business to call applicants you want to get, some of us still feel a little weird calling, it does not help the applicant in any way, but can help the program.
I AM NOT SAYING THAT PROGRAMS THAT CALL ARE BAD OR UNDERHANDED. THIS IS BUSINESS AND IN MANY WAYS IT SHOWS DEDICATION TO THEIR RESPECTIVE PROGRAMS.
But many programs look at their rank list (typically finalized on the last day of interviews) and contact those that are within their desired match range. What does that mean?
Interview 40 or so, rank 35 or so (that's right some applicants are so bad at the time of interview that we would rather scramble on matchday than match them.) The 'strongest' applicants are in the top 50% or less and your wish list is the first few applicants(=to your number of spots).
Bottom line: Every program has their own system, I estimate less than 50% call outside their number of applicants. The vast majority of programs match outside their top X (X=# of spots).
Hope this is helpful