Why does Siri not set Geofence reminders on iPhone when used in conjuction with an Exchange account?
After further research is seems as though Siri creates "Tasks" on my Exchange server, which don't allow geofencing. What is needed is an iCloud "Reminder", which does allow for Geofence reminders. You need to set up Reminders to use iCloud by default as follows:


Make sure your iCloud account is setup online, and enable the same
iCloud account on your iPhone.
Make sure that the notifications and calendars are syncing with
iCloud on your iPhone.




Next you will need to navigate to Settings >> Reminders:







Once these steps are completed the reminders functionality (with geofencing alerts) should work properly (even with Exchange). You will obviously need to designate Geo points via a contact entry with address information on the iPhone itself for this to work (i.e. Work, Home, etc..). There is a lot of good information on this question along with a trouble shooting process in this Apple forum thread located here. Please note that this process was tested on an iPhone 5 with iOS 6 (build 10A405) on an AT&amp;T cellular network.