There's no way to have a BB activated on 2 BES. There's a "trusted link" that's established between the BES and your BB during OTA activation and your BB can only have one of those at the same time.
I've managed during testing to have my BB linked to 2 BES (don't ask why or how ;)) and saw in "Security Options" that my IT policy and Desktop service both playing ping-pong between my 2 BES. Encryption wasn't working half the time (in fact, half the time the BB was connected to the second BES
![Smiley](http://www.blackberryforums.com/images/smilies/icon_smile.gif)
) It was kinda fun, though...
So, no, can't be done... BES and BIS, can't say... I never even tried BIS yet
Hope this helps