Outlook on Android and iOS now supports Office 365 shared calendars. Microsoft is rolling out a new update that will enable shared calendars for Office 365 accounts and allow users to sync all of their Office 365 accounts on their Android or iOS devices. The app will only support new shared calendars that are created after the new update:
We are rolling out a feature update that enables shared calendars to sync to mobile phones. This update will make it possible to sync all your Office 365 shared calendars to your mobile phone for any permission level (view, edit, or delegate permissions). In addition, you can now share a calendar or accept shared calendar invitations from Outlook on iOS and Android. Existing shared calendars will not be upgraded as part of this change, and they will continue to sync only to Outlook on the web, Windows, and Mac. Only shared calendars that are accepted after these changes are released will sync to mobile phones.