In BES 4.0 + Domino there is a domino database called "User Profiles" with a list of user and some characteristics and statistics. I wonder that in Exchange there is a similar DB also. You'll find there the info that yo're looking for.
This page: http://www.thegrims.com/berrystats/
tells how to make a web page with BB statistics.
MOre info: http://blackberryforums.com/showthread.php?t=10003