If you're on a Middlesex County system talkgroup and you have a hard patch between that and Somerset's Region 3 then the Somerset consoles ought to hear you just fine and you'll hear them just fine, there are no UHF-T channels between the two of you.
The DTV interference doesn't cause problems with Somerset's system/ wired infrastructure, it causes RF interference to units receiving and transmitting on those T-band channels. Conceptually it's similar to others trying to talk into the system from its geographic margins and having poor service whereas you're in a good coverage spot, except instead of the difference being location it is the frequency band you're on (Middlesex's 700MHz vs. Somerset's UHF-T).
Now I'm taking your word for it being a "hard patch," as in a direct wire/ microwave/ IP/ whatever link between the systems. If the actual connection relies upon transmitting into and receiving from Somerset's system on the UHF-T channels, even if from a console patch, then you indeed are at risk of adverse effects of the DTV tropo. So what I've written is rather speculative, you should go to your sys admin/ techs and present the concern and listen to their answers given the insight which they have into how it could/would be configured.