I used some as a secondary fermentation in an old ale I brewed up a while back. I fermented the main batch with Sac, then after a couple of weeks added the vial of Brett L to the primary fermenter and let it sit for another few months. It got a nice pellicle after a little bit, but never really went away. At that point I was getting worried about sitting on the yeast/trub for too much longer (probably paranoid), so I transferred to a secondary and just made sure I picked up some of the yeast trub from the primary. In secondary the brett made another nice pellicle, and I let it sit there for another few months until the Brett flavor was where I wanted it to be. It definitely gives off a farmhousey flavor, but I think there's a little more cherry to it than the regular Brett B, although that may be just me tasting it after reading about it. At this point its probably sat in the keg for a year now while I've been drinking it, and its still quite tasty, although I do need to finish it up to clear up a tap!
I haven't tried using it as a carbing yeast, but there are certainly people who do (along with Orval). I'd guess you'd probably get less Brett flavor out of it this way, but if you were able to let it go for a while you might reach the same levels. The benefit of the carboy is that you can taste it while it ages and cut it off once its hit a good spot. I'd also worry about not being certain how far down the Brett will take it in a bottle and wind up with bottle bombs (see paranoia above). If you've got the time and a spare carboy you don't mind tying up, toss it in as a secondary and let it do its thing.