I interviewed this past weekend (their last interview weekend), and the director told us they will be finalizing all decisions this week and next week as the class becomes more determined. He said only 12 students so far have committed to the ~60-70 slots they intend to fill.
I just got a Vanderbilt IGP interview offer yesterday and had the choice of 2 weekends -- March 14th or March 28th. I'm pretty positive there are earlier dates as well.
I recieved an email from the DGP saying I could track my status about a week after I submitted it (submitted on 12/14). I recieved my interview within a few days after that, so maybe it's automated once your application has been reviewed.