I think your right, but U. Chicago tends to notify on the later side of things, pretty close to March 1 and as late as March 7. The other three will probably contact top choices in a week or two.
For those curious about Notre Dame, I can confirm that according to the Admin. Assistant for doctoral admissions, all of the first choice applicants have been contacted. She claims that people usually come off the waitlist, so if you haven't heard consider yourself waitlisted.