I think we're seeing a discrete frequency come to life on all the new towers being populated at Metrolinx locations, obviously focusing on the rail stations over the bus depots. Once they go (no pun intended!) fully operational, I'm curious if they'll rebroadcast the mobile (train) transmissions across other towers or be truly pure simplex on a site by site basis.
There would however have to be some kind of automation to keep the mobile radios on the appropriate frequency if that's the case. There's a fair bit of microwave hardware on most of them, so site linking looks likely.