I've managed to open an ics file stored locally, and the UIDocumentInteractionController recognizes it the UTI as com.apple.ical.ics (which is expected). The data displays as I was hoping, for the most part:
I was under the impression from the docs that UIDocumentInteractionController would automatically recognize this ics file type and give some calendar-related options, however, there doesn't seem to be any way for me to add these events to my calendar from this view. Under the "Open in" menu, I see mail and dropbox as options, but not Calendar. If I email it to myself, I then can add the events from the mail app. Am I missing something with how this view works? Mobile Safari handles ics files in a similar way, except there will be an "Add all" button in the title bar. That's exactly how I thought this would behave. I'd prefer not to use EventKit at this point, since I'd just like it to mimic how safari handles the file.