updated 04:40 pm EDT, Thu October 27, 2011
Apple said to be aware of trouble
People are still finding themselves unable to access iCloud calendars through Google Calendar, complaints indicate. Users should be able to share iCloud calendars through a URL; trying to open the link with Google Calendar's "Add by URL" function, however, currently generates an error message: "Could not fetch the url because robots.txt prevents us from crawling the url." Apple has allegedly been aware of the problem since at least October 17th.
The issue reportedly doesn't exist when transferring data to other calendar sites like Yahoo Calendar. The only workaround may involve syncing indirectly, whether through a third-party service or a program like BusySync. Some other clues to the difficulty may be that iCloud calendar URLs are longer than those for MobileMe, and also no longer use an ICS extension.