Sharing Office 365 calendar with an iOS device
To share an Office 365 calendar with a non-EM user (such as a g.ucla.edu or non-ucla account), follow these steps:
Beware! Depending on the platform, you might import the current calendar rather than subscribe to it.
To subscribe, you want to copy the long url rather than “share” it.
Subscribe to ICS calendar in iOS
To get a calendar subscription, you need to subscribe as described here.
This procedure worked for me using the .ics link (rather than the .html link) on iOS 11.4.1