It can be seen more common requirements of pre-migration or post-migration tasks to perform,

Scenario 1: Re-populating previous data stored in PST files in to the new Exchange 2007 mailbox at Exchange server end by  Administrator.

Scenario2: Moving existing Mailbox data in to a PST file at Exchange server end by Administrator.

Although below mentioned cmdlets would be given by resources to perform these task using Exch 2007 Management Shell, it’s not that straight forward if the relevant permissions are not set to Administrator to perform these tasks on behalf of Mailbox Users.

Import PST data in to a Mailbox

Import-Mailbox -Identity <mailboxUser> -PSTFolderPath <PSTFileLocation>

Eg: Import-Mailbox -Identity Lakmal -PSTFolderPath C:2006.pst

Export Mailbox data in to a PST

Import-Mailbox -Identity <mailboxUser> -PSTFolderPath <pathToSavePST>

The point is once these cmdlets executed Exchange 2007 Management Shell stops with incomplete move as the screen shot below by default;

TIP : To avoid this the Administrator account (whatever the account used to perform the task) must be assigned with Extended Rights to have "Receive As" permission all before execute cmdlets. This is how it happens in below screen shot;

Get-MailboxDatabase -identity "Exchange Server NameFirst Storage GroupMailbox Database" | Add-ADPermission -user "Domain NameAdminAccountName" -ExtendedRights Receive-As

Upon the successfull completion of the cmdlet your Exchange 2007 environment is ready to Import/Export PST tasks. You will see now its moving without red stops halfway.

Hope this would be helpful somehow, Cheers!!!