Per this article:
Sources say the Cubs have been pushing the Tampa Bay Rays for a quick deal. The Rays were one of Bradley's top suitors last winter until the Cubs let the world know they had a three-year, $30 million offer on the table. The Rays loved Bradley's on-base magic and manager Joe Maddon is so self-assured -- to a fault -- he believed he could handle Bradley's unique personality as deftly as Texas Rangers manager Ron Washington did in 2008.
This is going to be one of those ongoing storylines. If this report is to be trusted, then the Rays would essentially trade contracts with the Cubs. They would pay Milton Bradley the same amount they were going to pay Pat Burrell, but if the Cubs covered some (or hopefully all) of Bradley's 2011 salary, the Rays would have an opt-out clause if Bradley acts up and murders a bat boy or six.
The added flexibility has to be at least somewhat attractive and Tommy covered this possibility a while back, here.