In this area, EDACS is certainly a dying breed. London's is gone, Sarnia's is still running, but has very little activity. Brantford is underway in their upgrade process, which basically leaves Kitchener-Waterloo and Chatham-Kent as the only remaining systems around here.
That being said, I've had no problems decoding Chatham or Brantford's ProVoice with DSD... so my hunch would be that Thunder Bay is either AEGIS or encrypted ProVoice.