No problems using N2 with bbb, although, I highly recommend tossing it after this season since it is a big cash grab, using the bbb method, you will spend 50% of what a cartrige costs over 1 season, and that does not include the other chemicals you would still need to use along side the N2.
N2 is really just supposed to let you run your pool on lower chlorine levels by using silver and copper as an anti algae supplement, but for what it costs, it's just not worth it.