Hmmmm.... I don't have any experience with programming, and by the looks of it, Event Sinks mean you need to program something to get this done.
I did find Add2Exchange, which could do the trick..... but I hate explaining that I need to spend another $695 just to get their shared calendar to sync to their Blackberries. If that is the case, it would actually be cheaper to replace their phones with Windows Mobile devices, which at least can use a user-shared calendar. (which would also work for me, i'd just create a domain account and share its calendar.
Ah well, sometimes you can't have the bread AND the butter as well. 
=> each person has his/her personal calendar that is synchronized with the google calendar.
=> the google calendar is synchronized with each person's blackberry
the sync between Google Calendar and the default Outlook calendar can be done by an application for PC called "Google Calendar Sync".
the sync between the primary Google Calendar of a google account and a Blackberry can be done by an application for Blackberry called "Google Mobile Sync".
I think there may be huge problems when all six sync tools act at the same type. the secretary can probably schedule the sync at different hours of the day, but it could be a pain in the neck.
The other solution in indeed the event sink that will sync a personal calendar with the public folder. It requires low level "VBA for Outlook" skills (meaning : can be done by any lazy developer in a week).
there is an even easier solution : don't use the public folder. the sync conflicts would be easier to cope with.
=> the Outlook calendar is synchronized with the owner's blackberry
=> each blackberry is synchronized with the google account.
The search box on top-right of this page is your true friend, and the public Knowledge Base too:
The 2 people I am talking about have laptops.... I am thinking for this to work the Google Calendar app will have to be running somewhere, and be synced by someone, which really isn't great in weekends (we run a 24/7 company) when the secretary isn't there...... Furthermore, however great Google may be, I rather not rely on a "free" application like that. We have to be SAS70 compliant, and BES 4.1 meets our security requirements, as well as Outlook Anywhere, which is ONLY offered using SSL, etc....
I really would want to run something in-house, behind the firewall, that will work to update their calendars, and really only have the BES communicate out to the Blackberries.
I know a few devs, so I may have to pay one of em to write an "event sink" to do the trick. Of course that also has its downfalls, for instance if Exchange Server 2007 SP2 would be released, and MS changes things so that the event sink app will no longer work.
Decissions, decissions.... bread, butter etc. I may just have to bite the bullet and buy Add2Exchange.
