This is one of the few threads that resembled the troubles i was having with annoying calendar notifications on my iphone. As stated above the "Shared Calendar Alerts" did not work for me either. My problem and final solution pertains to Google calendars, so this may not help many.
My digital life, for better or worse, is Google. My calendar, my work calendar, my family's and my wife's. Long story short i wanted her calendar on my phone so i could see her schedule. But all of her alerts that she set for her calendar reminders were passed on to me and popped up on my phone.
Here's the fix i found as it pertains to shared Google calendars. I had originally had her calendar set up as another mail account, but with the mail and contacts portion turned off. I went in and deleted this account. I went to Add Account > Other > Add Subscribed Calendar. In the Settings > Calendar Details of my wife's Google Calendar i got the ICAL private address. (Long private URL that ends in */basic.ics.) I put this in the Subscribed calendar and hit next.
Now i can see her calendar without the annoying alerts and pop-ups. Now it is under Shared Calendars and i have even more options for removing alarms and alerts.
I'm not sure if this will help everyone, but if you can find the ICAL *.ics address of the calendar you want to view from its provider this might be a fix. This had plagued me for a while so i had to post. If this post is better placed somewhere else, please advise.
Thanks,