Just restored my subscribed calendars on my 3rd Gen iPad running iOS 7.0.4 by turning off "Use SSL"... no problem.
Here's how:
1. Go to Settings
2. Tap on Mail, Contacts and Calendars
3. Click on Subscribed Calendars
4. For EACH subscribed calendar that is not appearing in your Calendar app:
- tap on the calendar name
- tap on the slider switch to turn off Use SSL
- tap Done
- there will be a slight pause while the calendar is verified and restored... done!
- you should see it when next in the Calendar app.
I've found that if you try to turn on SSL again, you can go to the Calendar app and then come back to the settings panel and you'll find that SSL is turned off again. So I'm guessing that once verified, you iOS device will know/detect if the calendar supports SSL or not.
Hope this helps!