Your are high:
-Blackberries do not under and circumstances delete application to make room. They do however delete phone logs, emails, and other records (starting with oldest first) if the device is running out of memory. To suggest a BB would wipe an app to make space is ludicrous.
-ATT does not let you install BB maps for one reason: it provides free access to GPS mapping. They do this so they can sell you Telenav. Mobile GMaps is a free GPS app. If they have a reason to preclude you from installing BB maps, they would use the same reason to preclude you from installing (or uninstalling) Mobile GMaps. So, why in the heck would you say, "...but not Mobile Gmaps"? That makes zero logical sense.
-The app does run, when it is on the device.
-Me out of space, even though that is irrelevant...no way: