We had a post a few weeks back about programs that notified students WAY late. There's no reason that a program can't contact students by the end of April (assuming that the application deadline was in January).
Reader A.E. is calling out UC-Davis:
Another school to add to the list of shame: UC Davis. The school did not get back to me until last week (rejection, naturally). I called them in late April out of sheer curiosity to see what happened, and was told that if I haven't received a letter yet, then I was *probably* on the wait list, but that the program could not be certain. My politely phrased inquiry regarding a fee refund was taken as a joke.