If you're experiencing new and altered calendar sharing behavior, this may just answer your questions. There was a recent change to the way the shared calendars of Google Apps will function when shared inside/outside a domain/organization.

See Google Help Forum thread here: http://www.google.com/support/forum/p/Calendar/thread?tid=1a7ddeed8...

In summary:

At Google, we've recently made sure the 'Only free/busy information (hide event details)'
sharing option applies to both primary and secondary calendars. When a domain admin has set Sharing options
to 'Only free/busy information (hide event details)', this should apply to all calendars, both primary and
secondary, Previously, the setting only applied to primary calendars, so we've corrected this, and the setting
now applies to secondary calendars as well. If you'd like to have your secondary calendars display calendar
information publicly, you'll need to ask your domain admin to change the setting to one of the
"Share all information..." options. Keep in mind that this setting will also apply to primary calendars,
however, so make sure this is okay with your domain.