You can definitely view other shared calendars using CalDAV. They can be accessed directly, or you can set up a CalDAV connection to your account, which will then include your calendars and ALL the shared calendars that you've mounted.
To be honest the variety of possibilities is a bit confusing, including which ones allow read/write and which ones are read only. A couple threads that already discuss the options are:
iPhone 3.0 and CalDAV What mobile devices support shared calendars