Export:

set-adserversettings -viewentireforest $true

new-mailboxexportrequest -mailbox “mailboxname” -Isarchive -filepath \\uncpath\archive.pst -mrsserver server

new-mailboxexportrequest -mailbox “mailboxname” -filepath \\uncpath\mailbox.pst -mrsserver server

Status:

get-mailboxexportrequest -mailbox “mailboxname” | Get-MailboxExportRequestStatistics

See http://www.stevieg.org/2010/07/using-the-exchange-2010-sp1-mailbox-export-features-for-mass-exports-to-pst/ for a mass export