What do I need a Data Plan for? - BlackBerryFAQ
In addition, many third-party apps require the BlackBerry data plan.
Note, however, unless your carrier is blocking the GPS on the BlackBerry, you should be able to get a latitude and longitude position fix as observable in options > advanced > GPS.
But you will need the BlackBerry data plan to use use BlackBerry Maps and BlackBerry Traffic, and possibly other mapping and navigation apps as well. Posted via BlackBerryForums.com Mobile