When migrating to a new (version of) Exchange this is how you can synchronize the Public Folders :
Start the exchange management shell and execute the following code :
C:\Program Files\Microsoft\Exchange Server\V14\Scripts>
-Server "Exchange 2007 PF server name" -TopPublicFolder "\"
-ServerToAdd "Exchange 2010 PF Server Name"
You should be able to do this using the Exchange Management Console but this often doesn’t work. After executing the above script you should be able to check and edit it again using the console although.