Howdy Bill!
The easiest way would probably be to use theĀ iCal Importer. You could post shared events to a Google Calendar feed. Or you could even have a dedicated site for posting shared events, and then have the other calendars import its iCal feed.
I want to be up front with you about our iCal Importer. The current version is actually suffering from a few bugs, mostly causing duplicate events. We are working hard on this right now and should most all of these problems resolved within 2 weeks. I just wanted to mention this because it is pretty unusual for such prominent bugs to be in the wild, and so it’s probably not something you would expect given your past experience with us. But rest assured we’re fixing it ASAP.
Does that sound like a good option?