Interesting system this. Back in Oz the NCB follows the owner ie you can have multiple vehicles all with the same NCB. Of course the flipside is if you lose it you will lose it on all vehicles. I assume over here if you have it on more than one vehicle, and it is specific to each, if you make a claim you only lose it on the relevant car?
I carried my NCB over from Australia (had to show docs to prove I had it). Also, when I switched from Aussie licence to UK there was a significant drop in the premium so may be worth considering as well.