Hi
You can go to route plan> route plan report
and you can find the "view in file" option (up/right corner)
This will creeate a csv file with all the dn's of your CCM including ip phones.
Or you can also use BAT export option to create a CSV of all the ip phones.
Neither way show if the devices are registered or not, but those are the closest options that I know to what you ask.
Regards
Pedro