Howdy Atul,
Using the iCal Importer it is possible to do basically that. You can already export events from one site as an iCal feed. The iCal Importer allows you to import them into another site.
In you case you might be interested in setting up a third site that combines the others. That way it is still possible to view the calendars separately if you want to, and then a third calendar will combine all of the events.
Does that sound like it might be what you’re looking for? If so, do you commonly use recurring events or event tickets? The main caveat with all of this is that iCal files do not contain all of the same information as our plugin, so an event ticket for instance would not transfer from one site to the other.
Cheers!
– Brook