I consider applicants who ask for sources to be the most sensible of all applicants.
Unfortunately the only sources I can offer on this are unofficial: the Bacc/MD thread has many posts from applicants not invited to interview for Bacc/MD but who were admitted to USC (some with scholarships) in the Jan/Feb wave, as well as others who did not hear about admission until March (and were admitted). Also search the USC forum for "New Applicant Toolkit." There are accepted student stats threads linked there that have posts (most in Jan/Feb) from Bacc/MD applicants - some interviewed for the program, some not.
Intuitively, remember that students who apply to these combined programs are some of the most accomplished in the nation, so certainly they would be excellent candidates for admission even if not selected for the 30 spots at USC (yes, there are only 30 spots
It would be great if you would give USC a call to ask this question of them and then come bnack here and tell us what they say - that would be much more useful to ease the minds of those applying to the program than my anecdotes.