I think this year is very special due to the change of applicant requirements. Maybe even adcom is still learning this new change.
However, I read the posts about this program intake 2017. One user alphabeta4 applied in R2 and got interview invitation on Dec 15 2016. Another one sunandsand also applied in R2 and invited for interview on Dec 23 2016. So, according to the very limited information above, and MIT announced R2 interview will be in Jan 2018, I guess interview invitation will be give separately to selected applicants in Dec. Maybe it is because the location. The school has to arrange so many preparations to conduct one good interview. But what makes me surprised is the school invited candidates on Dec 23 last year, which I think they should be on vacation on that day.
Anyway, I keep my fingers crossed for my good news.