I have already reproduced this in the public CiviCRM sandbox at:
Steps to reproduce:
1) Go to Events ... Manage Events http://drupal.demo.civicrm.org/civicrm/event/manage?reset=1
2) (I used Chrome) Right-click on the green ical image and choose "Copy Link Address"
3) Login to Google Calendar and choose "Other Calendars ... Add by URL" (This is located on the left side towards the bottom of the screen)
At this point everything seems fine, the new calendar appears in my Google Calendar populated with various events from CiviCRM. But nothing ever changes after this point in time.
if I add any new events to CiviCRM, they never show up in the Google Calendar that is a subscription to the CiviCRM iCal feed. ( I have waited weeks and nothing ever gets updated. Not only new events fail to show, changes to existing events also do not show)