they said that if a turret takes enough damage it will be disabled
EMP is an efficient way of disabling something, at the cost of it
not being damaged.
You dont have to run up to a defended turret and hack it, you dont have to throw 3 normal nades to damage it,
and you dont have to waste an entire clip shooting at it.
Ofcourse this is all speculation that it would even exist in Brink, but given its functionality in etqw, it wouldnt surprise me.