BES Express 5 upgrade
 

Hello
We are looking at upgrading our Exchange Server from 2007 to 2010. Currently we are using BPS 4.1.4.3 and I know I need to upgrade to BES Express 5 to work in Exchange 2010. I was wondering if it's possible to have both the BPS and BES server in the same organization and cut over one phone/one mailbox at a time. I was thinking of moving a mailbox over then reactivating their phone on the exchange 2010/BES Express 5 while keepiong the other mailboxes running on BPS/Exchange 2007. Has anyone tried this scenario?