Back in January 2017 I asked PSERN about encryption. Their response indicated that each agency will decide which - if any - talk groups would be encrypted.
I asked the Seattle Police Department (SPD) about their plans for encryption and received the following response:
Dear Mr. Caples, We received your online inquiry regarding the PSERN and encryptions. I have spoken to multiple individuals in the agency and the answer is as follows: SPD has not determined to what extent the department will encrypt its dispatch channels under the PSERN. With that being said, I was also informed that PSERN will not be fully operational until 2020 at the earliest. Please let me know if you have any additional questions. Sincerely, <redacted> Administrative Assistant, Communications
Thank you for your inquiry to the Seattle Police Department.