If they are using anything, I haven't found it yet. Bethel was a part time department for so long, they had no need for a private channel because there was only 1 cop on at any given time. Now there's usually two, but I don't think they use a private radio channel. Maybe they're using Nextels (or Sprint's version of them) or piggy-backing on something else.
Also, there is a radio tower behind the Bethel Fire station that has a business LTR Nexedge system on it from Baycomm (WQJV354). He leases talkgroups to fire and police on it so they could be on that also. I know the Upper Chi fire companies are using that system for their private comms.