That is what I figured. Because the restricted numbers include cell phone calls which are the same number of digits as land line calls, the only way to figure out what numbers are restricted are through the ARS Digits Dialed feature. Because this only uses COR for restricting call, there is no way to block this if the user has a valid account code. If you cannot turn off the ability to enter verified account codes at the phone, then there doesn't seem to be away to do what I want.
I guess I might have to just turn off external calls entirely from these phones. Thanks for your input though.