There is no direct sync but you can do so through scheduleworld.com (funambol/syncml). They have a working client for Thunderbird 2.0 & sunbird/lightning.
The blackberry client from funambol runs but is barely functional. Its a few revisions out of date with the syncml protocol.
funambol :: mobile open source
An alternative client for the BB is SyncJE but it isn't free.
Mozilla Sunbird Sync. Conduit 
