They'll know your undergraduate (and graduate) institution(s), along with your major fields of study. Your undergraduate GPA is not pertinent, and will not directly impact your ability to match into a residency.
While the majority of residencies do not ask for your undergraduate grades, some of the early match specialties ask for undergrad transcripts. The only one I'm sure of is neurosurgery. The other early match ones are urology, neurology, ENT, and plastics (combined). I'm not sure about them, but I think they might ask for it as well.
Also, you might be asked about your undergrad grades / honors during your interview as I was asked on 2 of mine.