It's basically a hold-over from when CNJ was the sub-class for BRD.

As far as how useful it is, it does have its time to shine. Mostly, though, if the BRD is using the LB, it's because crap has gone very downhill and the healers are focusing on keeping the tank up. LB3 is still a full rez, even coming from a BRD, so it's better to have the BRD activate it than to have a healer drop from healing the tank for as long as LB3 and recovery takes. It's not something you'll be using often, but when you save the day with it (without the healers dying to animation lock), it's awesome.