Just want to see what people think about this around here. The Tau FB group is incredibly biased and only a handful of us think it works the conservative way.

Coordinated Firepower: Whenever a unit from a Hunter Contingent selects a target in the shooting phase, any number of other units from the same Detachment who can still shoot, can add their firepower to the attack. These units must shoot the same target, resolving their shots as if they were single unit - This includes the use of markerlight abilities. When 3 or more units combine their firepower, the firing models add 1 to their ballistic skill.

The part in bold is the only contentious point I believe as everything else in the rule seems straightforward.

1st interpretation - When you select three units to fire for example, those units can all gain markerlight abilities if there are tokens in the target unit already. They gain +1 BS. That's all fine. The hot point is, say there is a Commander with the wargear that twin-links and allows ignores cover for his unit in one of those three units you picked. Do they all now gain those special abilities and USR's because they "count as" a single unit?

2nd interpretation - When you select units, you get the aforementioned marker lights and +1BS. That's it.