Does OS X Calendar (née iCal) support RDATE?
I have not run exhaustive tests but empirically I have concluded that Apple products do not implement the RDATE recurrence rule.  

Apple products do appear to implement the RRULE but only a limited subset of this.  The extent to which the RRULE is supported might be deduced from the options available for setting recurring events in Apple apps.  It should be possible to support simple patterns (every day, every week, every 2 weeks, every month, every year) but probably not more complex patterns using BYMONTHDAY, BYYEARDAY, BYWEEKNO, BYMONTH, BYSETPOS.

I've noticed that Google Calendar might display a full recurrence set whereas an Apple device that is synced from that calendar will only show the first event.

I would welcome a more authoritative answer.