Way back when, the Barrie area was part of the Owen Sound MTO's area of jurisdiction.
I suspect that since the Barrie Enforcement guys were dispatched by Owen Sound, they came under the London Comm Centre's area of responsibility.
I believe Downsview MTO handled the GTA/Golden Horseshoe area so Orillia Comm Centre handles them.
I did get a quick peek at an MTO radio once and I believe each area had it's own Ops and Tac channels. Something along the line of HALOPS and HALTC for Halton.
Not sure what PT1 would be. Perhaps some sort of Provincial Tactical 1 for the London area? I suspect they would have some Common Channels at the beginning of their Zones much like Ministry of Corrections and Ministry of Health.
Keep in mind that many channels are patched together at once and unless you're watching it with something like Trunker, it's hard to really tell what talkgroup they're on.