Alright, for those curious, here are some interesting values regarding the 2017-2018 cohort of interviewees at a top private medical school (n > 500):
Attended Canadian college: 3%
Attended a college ranked only regionally by US News: 3%
Was the only interviewee from their college for the year: 13%
Among schools receiving a US News national rank...
US News ranked 1-25: 68% of interviewed students
US News ranked 26-50: 13%
US News ranked 51-75: 8%
US News ranked 76-100: 3%
US News ranked from 101+: 9%
The best represented colleges...
Hopkins, Harvard, Duke, Stanford, UCLA, Yale, Penn, Brown, Cornell, Dartmouth, UNC, Princeton, WashU, USC, Berkeley, U Chicago, Columbia. These 17 together provided the majority (54%) of interviewees.
Interesting aside not from this dataset: While the above 17 produced most interviewees, it's still only a very small minority of the yearly premeds generated from these schools. We're talking ~300 interviewees from the above, when in 2016 there were ~6,400 total MD applicants from these same 17 colleges.
Universities which were ranked in the top 25 but did not provide any interviewees:
Caltech, Carnegie Mellon