Seems to me it can do offline google maps though, if I recall correctly as it has been a while since I used it, that the process isn't straight-forward. Not impossible, just not simple.
Posted from my CrackBerry at wapforums.crackberry.com
You can upload maps when on WiFi using the native BB Maps App and keep it running.
After you disconnect the WiFi, you can still use the maps, but you can't search for places.