Just as an FYI ...
When I interviewed late Nov on-campus, adcom member asked me if I was R1 or R2 applicant (!). And when I told him that I was R1, he said that in that case, they would put my file on some urgent or express (I am able to recollect the exact word) queue for review.
So my guess is that they have reviewed all the files, except for those from folks who are yet to be interviewed, and have a fairly decent idea on whom they want admit. And those calls should not go on beyond Friday 5 PM CST. The trickling that we will see are for those who have had their interview in Dec or something.
Just my 2 cents anyway...