CalDav / iOS / OS X 10.7

[ThatOtherGuy435]

I seem to be having a fairly major problem with ZCS 8.0.2, iOS / OSX and calendars.
Because of the way that things were set up before we switched to Zimbra (small medical office), our 'shared calendar' is actually a single user account that multiple users log into with iOS devices and iCal OSX devices. The problem is that many, many (thousands and climbing) hidden calendars are being silently created by iOS devices as they connect, with what look like random strings in the format XXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX. The final caldav url (pulled from mailbox.log) ends up looking somewhat like this:
I">https://192.168.2.12:443/dav/caluser%40 ... FA62A1615/.
I can't figure out why these are being created and how to remove them. They don't show in the Web UI, they don't show in Zimbra Desktop, they don't show in iCal, and they don't show on the iPhones.
Full MKCALENDAR even from mailbox.log:

2013-01-24 07:02:42,751 INFO [qtp1456226908-5843:https://192.168.2.12:443/dav/caluser%40 ... 6BAF04527/] [aname=caluser@domain-name.com;ip=98.250.72.32;ua=iOS/5.1.1 (9B206) dataaccessd/1.0;] dav - DavServlet operation MKCALENDAR to /home/caluser@domain-name.com/84ABC527-F14F-47B0-9A88-9956BAF04527/ (depth: zero) finished in 268ms
Full zmcontrol -v string:

Release 8.0.2.GA.5569.UBUNTU12.64 UBUNTU12_64 FOSS edition
The number of hidden calendars is getting to the point where iCal actually times out on updating, and gives the spinning wheel of doom.
Is there a way to get iOS to stop doing these? Failing that, is there a way to access and clear out the hidden calendars via command line, so it can be scripted?
Thanks,

A tremendously frustrated sysadmin

[ThatOtherGuy435]

Update with more information, though no solution:
iOS isn't creating calendars, it seems to be creating Task lists, even though the account is not under a CoS that allows tasks. Explicitly allowing Tasks for that calshare user lets me see the hundreds and hundreds of empty tasks via Webmail.
Any thoughts on why iOS seems hellbent on registering so many GUIDs as tasks?

[myriad]

Looks like Zimbra 8 has broken iCal.