Note: You must be using the Outlook app for this to work.
Share the Shared Mailbox calendar through OWA to the individual who wishes to access it.
Then follow these steps:
- Open the sharing invitation on your phone in the Outlook app.
- In the sharing invitation find the button that says Accept and tap it. Then click View.
- Click on the Menu button and select the Shared Mailbox calendar. This should open the calendar on your phone.