I just ran the feed through an online validator (http://icalvalid.cloudapp.net/?id=634772542201969681) and it seems to have some major problems:
- The DESCRIPTION property is invalid; commas must be escaped in text fields.
- Line endings must be a Carriage Return/Line Feed (CRLF) pair.
- The VERSION property should be the first property on the calendar. Some calendar clients cannot properly parse the calendar otherwise.
- Empty lines are not compatible with all applications.
This is probably the reason why it's not working in GCal.