Timely events calendar offers full ics/ical support. You can import events from other Website calendars and offer users the ability to subscribe to your events calendar.
Importing and exporting iCalendar (.ics) feeds is one of the strongest features of the All-in-One Event Calendar system. Enter an event on one site and you can have it appear automatically in another website’s calendar. You can even send events from a specific category or tag (or combination of categories and tags).