Able to add subscribed Calendar from Exchange 2010 mailbox/user OK to current OS iPhone
Able to see events on the subscribed Calendar from the iphone
When Calendar invite was published from Users mailbox, all rights were granted.
User tries to add an event to the subscribed Calendar (from the iphone) but that subscribed Calendar does not show as an available calendar to add to ! The original iCloud and Exchange ActiveSync accounts do, just not the 3rd subscribed calendar.