Listowel? Are you sure? I monitor Listowel regularly on my drives north and haven't seen tg 8624 (1OPS36 Nottawasaga) show up on that site. Talkgroups I have seen (and confirmed with trunker) on the Listowel site are 8416 (1OPS14 Wellington), 8384 (1OPS12 Sebringville), 8304 (1OPS07 Huron) and occaisionally talkgroups for areas further north (South Bruce, Bruce, Grey County).
Perhaps Nottawasaga is patched with another talkgroup, maybe 1OPS33 Huronia or 1OPS31 Collingwood. Me, I'd listen for specific softids (the 1Lima softids are Nottawasaga cars) in the communications on whatever talkgroup shows up on Primrose, it being the closest site to the Nottawasaga area. Perhaps Edgar is a good bet too.