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Based on the current situation, once your tenant (Office 365 pre-upgrade) upgrade to Office 365, you can create public folder which can be shown in Outlook 2013. Currently, Office 365 pre-upgrade does not support public folder because it is on premise feature. So, you can use the shared mailbox instead of public folder now.
For your reference:
Set Up a Shared Mailbox
How are things going? Do you have any updates about the issue?
Public Folders appear to be supported and available in Office365. I set mine up successfully in the Admin page. But the Outlook client are unable to view/display the Public Folders. Where are they? Outlook versions 2007 SP3 and 2010 SP2, all patches and updates applied.
First, you have to make sure you are the Owner of the public folder.
Then, after you open the Outlook 2010, Press Ctrl+6 to see Public Folders in the Folder Pane. You will see public folder like the picture below.