Gaussian proc in Tactics?

How would the Chance for Build Up 5% proc work if it were in the Tactics power?

And, how would it work in a more generic Build Up power that already had buildup?

Powers such as Tactics trigger procs once every 10s. So, every ten seconds, there's a 5% chance of the effect.
In click powers, such as normal Build Up, every time you fire off the power, there's a 5% chance that the effect occurs.

It should be noted that this will change somewhat in I24. All procs in the game are moving to the PPM-based system. For now though, that's how it works.

post i24 it may be more beneficial to put into BU because the store bought version is 1 PPM so it will essentially always have 90% chance to go off

in toggle it will still check only once every 10 sec, so in tactics it would have a 60% chance to go off every 10 sec (rough estimate)

How long does it last? I can't find that information anywhere. Are all procs going to be 60 or 120, or is this a 10 second benefit?

The GSFC proc gives a 5 second boost.

The best place to put it (IMO) is Aim or Build Up (or the fancy BU clones in sets like Titan Weapons and Staff), where even slotted, the recharge will be high enough that you have a capped 90% chance of it proccing, so that you almost always get a "double build up".