I have a few friends at IIIT Nagpur, so I think I can give a valid answer for this. IIIT Nagpur does not accept MHCET scores. IIIT Nagpur is a national institute and comes under the purview of Ministry of Human Resource Development (MHRD), the Government of India (GoI), and not under the Directorate of Technical Education (DTE), Maharashtra.

According to the rules, IIIT Nagpur accepts only JEE (Mains) score for admission based on its All India Rank. Even it does not have a state quota like NITs (50% seats reserved for home state students). So admission is purely based on your rank at the national level in JEE (Mains).