We use Google Apps for our business email. Recently we've been migrating our old CalDAV server to Google Calendars. Here are a couple of tips. All of these tips presume you've already set up Google Apps for your domain, configured your users and set up Google Calendars in iCal.

Migrating a calendar

1. In iCal highlight your old CalDAV calendar.
2. File > Export > Export... to your desktop.
3. File > Import > Import... from your exported file.
4. Select your primary Google calendar as the destination.

Syncing delegates with an iPhone

Delegates are calendars owned by other people in your organisation that you have viewing and/or editing rights over. Delegates work well in iCal (visit the Delegation tab of the Accounts preferences. But require an additional step on the iPhone.

1. Set up the iPhone using the Gmail profile (rather than Exchange). Exchange may work too but this is not our scenario.
2. While logged in to your Google account on your computer visit this URL (replacing the domain in [square brackets] with your own - also remove the square brackets) and select the delegates you wish to see on your iPhone. https://www.google.com/calendar/hosted/[mydomain.com]/iphoneselect

http://www.google.com/support/mobile/bin/answer.py?hl=en&answer=151674