Hi Aaron. Have tried this. Unfortunately I'm not having the same results. None of my calendars can be viewed in Office 365. I've also set up a 'testing' calendar. The url is below if you want to test it (it contains an event for today (5th march) Thanks
webcal://p05-calendarws.icloud.com/ca/subscribe/1/aM3jvb3n0vi-FBHOZpRA4RJnclpwIbf6YB3WnrjvmKVL6_gP00emLidKQ_M2O1AFePweHccjGMywHN1tg9gkiIru38RdyE0tDDe-pMl_z34