I've exported a Public Folder (on Exchange 2010), that holds reserverations for a conference room to a .pst file from Outlook 2013. I've tried to import this calendar into a Room Mailbox (Exchange 2013), and it seems to complete, but the calendar is not updated. 

Now I'm trying to run this command from Exchange 2013 powershell and it's stuck in queued status. The .pst is only 6MB.

[PS] C:\Windows\system32>New-MailboxImportRequest -Mailbox "SmallConfRoom" -IncludeFolders "#Calendar#" -FilePath \\Exchange2013\e$\Imported\SmallConfRoom.pst

Just be patient.

Or, if there's just one of these, just use Outlook drag-and-drop.  Open the PST calendar in list view so you can see all the items and drag them all into the mailbox calendar.

That worked perfect. Thanks again Ed.