Does anyone know if the BB Map uses any data while using a GPS?

I would believe so.

using a bluetooth gps receiver with your pearl has NOTHING to do with the physical maps displayed on your screen. in other words, those maps will come from the BB maps server (or that of whatever mapping software you're using) regardless of whether you're using a gps receiver.

the gps ONLY tells your phone EXACTLY what the co ordinates are of its current location, and your software on the phone will pull maps via the internet and also have other features (ie directions, current speed, etc.).

so yes, it does pull data still. the gps, again, has NOTHING to do with how the actual maps are displayed on your screen

Yes but see my tips page

Stinsonddog's Blackberry GPS Review

BBMaps uses scalable vector maps which use less data than bitmaps.