Try using a file manager (you may need to download a 3rd party manager such as Astro or ES File Explorer) and go to /system/media/audio. In there you should find a handful of folders but the 2 you should be interested in would be /notifications and /ringtones. Drop your BB files in them and your media player should ignore them.
I'll also note (while we are in those folders) that you can delete or rename the camera click sound here too. In the /ui folder simply rename camera_click.ogg to camera_click.ogg.bak or something similiar.
Hopefully I didn't steer you to far off course, I'm using a Moto Admiral on Sprint so I'm just guessing that the file structure is similiar.