The 900MHz P25 system is ONLY for Toronto Hydro. The remaining users from the analog system (Works, Water, Transportation, etc) are on the new MBC Tier 3 system (900MHz).
Interestingly enough, the approval process for the 900MHz P25 system was contingent on the other users joining the system to share the costs. A comparison was made and it was determined it would be financially better to put all users on the P25 system as they could then reduce the number of cellphones issued as well.
Instead, now we have Toronto Hydro that bankrolled the entire system, and are now forced to pay for it themselves, because the other users contracted Mobile to build out a different system for them - for a lower per-radio airtime fee.