Everything needed for multiple event synch'ing is there - ref-timezones, acs-events with timezone foreign keys, etc.
What's mostly needed is to make the calendar package bright about timezones. Once that's done, it wouldn't be too difficult to extract that and build the timezone definitions and references required in iCalendar format.
The single event synch stuff only works because after experimentation I figured out that in practice Outlook only requires timezone info for recurring, not single, events.
It's been literally 8 or so months since I read the iCalendar spec by I think timezone defs are in theory required, Outlook's just a bit more forgiving so we were able to slip in that feature without fairly large-scale rewriting of the ACES calendar package.
