The only real concern you should have is with any existing IT Policy from Company A. If / when you leave and take the BB with you ask to have a Blank or empty IT Policy assigned to your deivce. Check out this post
to remove the IT Policy if you can't get Company A to send you an empty one.
That said, other than wiping the device for good measure before going to the new BES, I'd upgrade the OS too ... thats it!