As per the trends of last few years, NITIE Mumbai GATE cutoff stays around 700, for general category students. A score of above 700, is likely to get you an interview call from NITIE. The cutoff is lower for students of other categories.
For final selection, NITIE considers GD-PI performance along with GATE score.
A few of my friends graduated from NITIE Mumbai so I think I can give you some insight regarding the admission procedure there.
The GATE examination score required to be on the shortlist to NITIE Mumbai depends on the entire batch who has given the GATE examination and also on the entire candidates who applied for admissions at NITIE.
Group Discussion (GD) and Personal Interview (PI) holds weight as the shortlisted candidates are selected here.
On average, I would say 99 percent is safe. The percent required in a PI depends on the reservation category too.