Hi All,
I had this issue and found the answer that works for all my shared calendars over in the iCal section. There are assumptions made in the workaround though:
1. User is sharing another user's calendar AND doesn't require editing rights (just wants to view the calendar).
2. User doesn't want to see the shared calendar's notifications when they make changes.
3. Apple's use of the term "Public" in the sharing of the calendar doesn't bother you. The Calendar is only available 'publicly' if they have the url. You still have to send an invitation to the shared party and the URL generated for the calendar is not something that could be typically stumbled upon IMHO. The URL for my shared calendars are more than 150 characters long, but it still may an issue to some users.
That said, and Credit to jdubyaelliott who says:
"What I have done as a work-around which seems to work on both OS X and iOS is to have the person change from sharing the calendar with users to making it a public calendar to which others can subscribe. In order to make this change effectively, you first have to have the person sharing their calender REMOVE the individuals who are sharing the calender, THEN close the dialogue box to confirm. After that they can then publish the calendar and invite those they choose. When the subsribers accept the link, they need to be sure to check the "remove alarms" option. The only drawback here is that there is no way that a subscriber can edit the published calendar. Only the owner can do it. That's actually not a bad thing, but just be aware of that."
Here is a link to jdubyaelliott's answer - https://discussions.apple.com/thread/5191233?answerId=22600482022#22600482022
Hope this helps!
Jamy