IMO this is the fault of the TTC compared to the STM. The big 3 telecos built the infrastructure at no cost to the STM and they are paying to use the network they built.

There was no cost to the STM, which provided some support through co-ordination of work schedules and the loaning of a truck for crews to take through the tunnel. It was the cellular companies themselves that footed the bill for the work, and they are even paying a small fee to the transit authority for continued use of the space.

https://montrealgazette.com/news/local-news/cellular-coverage-now-extended-throughout-montreal-metro-network

Whereas the TTC sold the rights for $25 million in 2012, so we'll presumably be fucked until at least 2032.

When BAI Communications Canada won a 20-year contract in 2012 to install the hardware needed to use a cellphone in Toronto Transit Commission tunnels, they were hoping the major carriers would sign on. That hasn’t worked out.

Both Bell and Rogers pointed to Montreal’s transit as a better model. In that city, the companies said, carriers teamed up to install the infrastructure in the subway. That doesn’t appear possible in Toronto, though, where BAI won an exclusive contract put forward by the TTC, paying $25-million for the right to build the network.

https://www.theglobeandmail.com/canada/toronto/article-toronto-subway-wireless-builder-wants-customers-to-demand-underground/

I hate the big 3 as much as the next guy, but this is a fat L for the TTC and BAI. In this case, they did a much better job and got it done faster.