X1536,
Lambton County EMS uses Bell Fleetnet towers in Sarnia (tower 31) and Ipperwash (tower 27), it might also be a good idea to program London(18), Chatham(16) and Wardsville(19) since they are close. For the TG numbers use the ones listed under Wallaceburg CACC, they control ambulance dispatch for Chatham-Kent and Lambton Counties.
For the City of Sarnia program the Sarnia-Lambton EDACS system, that will also give you FD for the City and County.
With that setup you should get every communication for EMS in Sarnia-Lambton and maybe Chatham-Kent, Since I can pick up Lambton County from Chatham.
Also here in Chatham-Kent, Sunparlour Medical Services handles EMS, it might be the same there.