Exchange 2003/2010 co-existence and shared mailboxes

Just to confirm something:

1. When a mailbox is moved to Exchange 2010, if a shared mailbox is attached which sits on Exchange 2003 does Outlook 2010 handle this differently to Outlook 2003 or do both clients mark the mailbox as unavailable until it is moved to 2010?
2. Is there a tool available for helping to discover which mailboxes are shared mailboxes under 2003?  In an ideal world all shared mailboxes would have an AD group, but in this case the mailbox management has been somewhat lacking and it is proving a mission to find the shared mailboxes