If you Understand how Zonal Protection of HVA works then you will know that the Army / CRPF and J&K Police, SOG, MI, SG are all part of the Security Protocols. There are Inner Cordons, Outer Cordons going out to 5 , 10 KM radius. The Army will also be doubling its Patrols and ISR further out from the Event and doing preemptive Screening and Interdiction operations as well.
MARCOS is on the water - you have a better unit to do that?
NSG is the Inner most Cordon and will provide EVAC in an emergency - you have a unit with better Shooters for a High Civilian Densitity AO in the Army? PS NSG has the best urban counter Snipers in the business.
Then you will also have other covert security that you will never see - JK S0G/SG/SF/MI
I am even willing to bet that SPG observers are also there providing their inputs in scanning for possible threat areas and set up defensive structures (snipers, Suicde Bombers, Drones etc etc)
Everything works in an Ecosystem.