NITIE offers admission based on CAT and GATE scores. Having a few friends from the institute, I think I can answer this question. NITIE usually considers more on GATE scores rather than the marks. As it has been observed that the students come from a varied educational background and thus the marks obtained by the applicant varies a lot depending on their educational background.
For instance, the highest marks obtained by a mechanical student go up to 95 and above while that of electronics, it is around 80. Thus one can see the difference in marks of the students obtained in both of the streams. Thus, to neutralize this variation, the GATE score is considered.
For an open category student, a GATE score of 700 and above will get them a call from NITIE.