No idea about priming w/brown sugar, but I recently brewed the Dogfish Head Indian Nut Brown clone from the latest issue of byo which uses carmelized brown sugar in the mash. As luck would have it, we recently had our 6%abv cap lifted here in NC and I found this beer (7.2%) at a grocery store and bought some to sample. It prominently lists brown sugar as an ingredient and flavoring component, but courtesy of this *#$@ cold I can't taste a thing.
I suppose the safe thing to do would be to prime a sixer or so with the brown sugar, and then the rest of the batch with your normal priming sugar just as an experiment.