Will free/busy information be immediately available in a Same Site Same Org Migration?
Exchange Migrator 2.2 SP1
Exchange Migrator 2.3
Exchange Migrator does not migrate the Free/Busy public folder information. According to Microsoft, Public Folders and Free/Busy information can be replicated and rehomed using native Microsoft Exchange Administrator.
The following Microsoft KB article contains detailed steps on how to accomplish this:
316886 - HOW TO: Migrate from Exchange Server 5.5 to Exchange 2000 Server
Use this link Migration of Mailboxes and Public Folders or select it from the link list "IN THIS TASK" within the Microsoft article.