Hi Steve,
As far as I know, the old Outlook identities will saved in your computer. You can access them to export to .olm files and move to the new Outlook for Mac.
However, since this feature is related to the Outlook for Mac client and our forum focuses on Office 365 Online services, we may not provide further assistance on your issue. In this situation, I suggest you post this question with the detailed information in the Office for Mac forum below for more professional suggestions and information:
http://answers.microsoft.com/en-us/mac/forum/macoffice2011-macoutlook?sort=lastreplydate&dir=desc&tab=Threads&status=&mod=&modAge=&advFil=&postedAfter=&postedBefore=&threadType=All&tm=1416727742862
Thanks for your time and understanding.
Best regards,
Kid Yang