He is not talking about loading another OS on the blackberry. Yes you can either download desktop manager for mac or use pocketmac. You cannot sync your contacts, etc. with mobileme.
Desktop Manager:
BlackBerry - Desktop Software for Mac
Pocketmac:
PocketMac -- Sync Macintosh Contacts, Calendars, Tasks, Ringtones, EMail & More To BlackBerry, Pocket PC, Smartphone, iPhone, and much more... | Call (619) 739-4027