I was complete at Tufts in late August, received the invite in mid-October. You can PM me if you want stats, but I have a very high GPA from a well-known undergrad, very high MCAT, solid ECs, excellent LORs, and I live in Boston now.
Did you say anything in the "Why Tufts?" (including why Boston) essay? I think it helps if they think you actually have a particular interest in Tufts, as opposed to med school in general. Also, they start interviewing people later than most schools, and interview through April... so at this point, no news is probably good news, I wouldn't worry about it.