The 10 days is only for ADP and not DES or AES. I don't think that ADP has taken off that much in popularity, not like DES, to acquire the tools or knowledge. And from what I have seen in CPS I don't think you can OTAR ADP as it is programmed into a CPS field most of the time.
Also the research is on the conventional side of the house. On a TRS, either a 3600 or APCO25, when you employ encryption the ability to make a clear call on a talk-group that is strapped for secure is impossible. And even using a different key will not allow the rogue user to be able to communicate with valid users as they will not be able to hear each other.
The paper is not all inclusive, especially where trunking systems are employed that create additional layers of protection. Conventional is very easy to manipulate and the more experienced technical users are well aware of it. The most important thing is that the end user devices are properly programmed and secure channels are strapped secure only. If a radio looses its keys it should be taken out of service and a loaner radio supplied unti it can be re-keyed by a keyloader or OTAR.