Yes, I do this all the time.
First: Create the shared mailbox.
Second: Give your self full perms to it and simply COPY all the items in the public folder to it via Outlook or export to a pst and import to the shared mailbox
Third : Get all SMTP addresses associated with the Mail-enabled Public Folder :
(Get-MailPublicFolder <EmailAddressofFolder>).EmailAddresses
Fourth: Mail-Disable the Public Folder:
Disable-MailPublicFolder <EmailAddressofFolder>
Fifth: Add the email addresses from Step 3 to the new shared maibox.
and you are done. ( Give any one who needs full and send as access to the shared maibox)