Many schools have a prescribed number of official interview sessions and a prescribed number of interview positions for those designated sessions. And these numbers and dates remain highly consistant from year to year.
If the school you are interested in has (early or mid) January interview sessions, then it is very likely that those notifications will be sent sometime in December, if not already. I know for a fact that certain schools have electronic notifications that go out in mid-December (around the 15th).
However, as previously noted, it is unlikely that contact would be made on or immediately around a major Holiday like Christmas. An Admissions staff hiatus will coincide with whatever their normal work schedule or University schedule is. And typically that would be a few days right around Christmas and a few days right around New Years - maybe less, maybe more.
For logistical ease and annual consistency, most schools do not continue to hand out interviews erratically until acceptance quotas are met (presuming the term quota just means until the class is full). Most schools, as noted, have a fairly accurate, prescribed number of interview slots - a number determined based upon years of statistical analysis to yield an adequate pool of candidates with which a school can generate a number of acceptances and alternates, if needed.
I am sure the specific interview dates with regards to UCSF can be found online or on these forums. You could also email the school and find out directly.
Good luck.
