Yes, you can get into IITs and IISc if you write Gate exam in XE (Engineering Sciences) but you will have to consider one thing in your mind that all specializations have their own criteria so before you apply its better to go through the eligibility as the eligibility for M.Tech specialization should match the GATE paper attempted. Also, if you talk about their cut offs then kindly mention which particular course and IITs you are asking for as it varies accordingly or you can go through the below given cut offs -

IISC Cut off

IITs Cut off

Hope this helps!!!