How to view public Exchange calendars from iCal?

In my company, people use shared Exchange calendars to organize their work. They see all the public calendars in Exchange after they login. Sadly, this doesn't work for me on Mac: after adding the Exchange account in System Preferences I see only my own Exchange calendar and none of the shared ones. I read [here](http://one.utsa.edu/sites/oit/OITConnect/mac/Pages/exchange_shared_calendars.aspx) about using delegation, but I don't know what e-mail to type there, as others see these calendars just as "public". Any hints?