Group Burst Run Efficiency 1 (Source)
Group Burst Run Efficiency
Essentially this skill reduces the everyone's cost to use Burst Run. I do not yet have Mobility IV so I don't know how low the cost gets. But at +60 it's +10 better than master scout. I suspect suspect the cap is at +100 but that's a wild arse guess. I suspect any Explore IV scouts (+40) with group BRE (+60) might be able to Burst Run with 0 HAM costs. Burst run efficiency is a percentage reduction in the cost of a burst run. So at +100 your burst run is 100% less cost, or free. This does not modify the amount of time you can run or how long it takes to get the run back. It only modifies the cost.
On the surface this might seem useful for speeding long planet wide marches. But the time it takes for you to be able to Burst again after running is like 5 minutes or so. In that time people's mind and action are going to regenerate to full on their own. The /retreat skill (Tactics III - provides a short group burst run, squad-leader excluded) is about the only thing we have for actually speeding long marches until they impliment /forcedmarch.
I think Group BRE's only value is allowing groupmates to still be able to burst run out of danger when their HAMs are deathly low. Ususally most people will try to escape before it comes to that, or at the higher level battles it won't come to that because high mobs can one hit kill. I don't think it will be a bonus that is taken advantage much if at all, but when it is used hopefully it saves a life.