I wanted to make that post on its own so that it wouldn't be missed or misunderstood.
Now, back to your issue. The problem is that when coverage is set to SmartZone (to reiterate, SmartZone and SmartZone OmniLink are essentially the same thing when the system has only one zone/RFSS as Somerset does), the radio is aware of the adjacent site messages on the control channel. So even if you have just the UHF control channels programmed in the UHF "system", and just 700 control channels in the 700 "system"...the radio is going to know about the other cell once it starts decoding either control channel.
The trouble with that is if the radio decides it has a better signal on 700 instead of UHF, or vice versa. So even if you're parked on a conventional channel that is calling up a scan list full of UHF talkgroups, the radio can jump over to the 700 control channel and you won't hear any activity.
There really is no perfect solution. As I mentioned much earlier in the thread, the radio doesn't care about the Preferred Sites parameter in the trunking personalities, as least not when I tested it a few months ago. It's certainly worth a shot to set that up, who knows maybe it'll work for you.
Go into each trunking personality, and scroll down to the very bottom. I would suggest blocking the other cell. So for all of the UHF personalities, set the Site List Type to Blocked, then change the Site ID to 4 (the 700 Site ID). Do the same for the 700 personalities, except block Site ID 3 (UHF).
You may also have to tweak some of the RSSI settings in Trunking Wide to make the radio less prone to switching cells based on the signal strength. Maybe lower the SmartZone RSSI Threshold values from the defaults to 20, 30, 40, 50 (decimal values, first column). Disable Strong Signal Roaming as well if it's enabled.
Also in each Trunking Personality, disable Non-Adjacent Site Search if enabled.
And finally, go through each system and all personalities with a fine tooth comb and verify that you have only the UHF control channels programmed for the UHF system, and only 700 for the 700 system. Make sure each personality is assigned to the proper system and you didn't accidentally assign a block of UHF talkgroups to the 700 system. Etc.