RDC covered the three fire departments in Trumbull (Trumbull Center, Nichols, Long Hill) Trumbull EMS, Easton Fire and I believe East EMS as well (that may have been SW-CMED already not sure) The fire departments were all on 33.56 with each of the Trumbull Departments utilizing their own cross band repeaters and / or base transceivers to the low band (TCFD has a VHF repeater linked to the VHF low-band, not sure hose Long Hill or Nichols used their assigned UHF frequencies if they still do). Easton Fire was only 33.56 as far as I know and Trumbull EMS and East EMS were on VHF-high.
As for C-MED to PD, its call direct private phone lines between each other for communication plus I think PD has the FD / EMS frequencies in their dispatch centers, which I would have to confirm.
SW-CMED does dispatch some EMS units Like Monroe EMS over MED 2 as a broadcast / simulcast(might be for the regional medics too).