Basically the issue is that when Users associated with Extension Mobility subscribes to services through the CCMuser page, these services will not be retained after another user has logged in and out of this phone.
This is because subsribing to the services using the CCMuser page updates the SEPxxxxxxxxx.cnf file, it does not update the ADPxxxxxxxx.cnf file. When the user logges out of the phone, the CM uses the ADPxxxxxx.cnf file to put the current device setting back on the phone, therefore, any services configured through the CCMuser page is not retained.
This does not happen when the CM administrator defines and configures the services for the ip phones.