"Trinity Wtby" is the channel that Waterbury Division and Cheshire cars are dispatched on. These cars will also respond to Prospect. The two generic "Trinity EMS" channels seem to be extras used by cars on transfers to or out of St. Francis, etc. but I can't confirm that. Maybe someone else knows exactly what they're used for.
Torrington and Stafford used to share a talkgroup. And another was their Chaircar talkgroup. Which is no longer.. They may have combined Stafford and Hartford