I searched the tau tactics thread but didn't see anything refering to 8th edition rules reagrding multi-trackers in the charge phase.
I'm not mistaken that units with a multi tracker get to re-roll ones on their overwatch, right? While modifiers can never change the target number to anything other than a 6, re-rolls still work as it's another shooting rule.
Just realizing that this might be the case. An extra bonus if you don't take the counterfire defense system.
And just to get it out of the way. I'm going to assume it doesn't apply to melee weapons, unlike the advanced targeting system, as it states "firing weapon". But would it apply to pistols? …like the flechette pod.