I'm also wondering if the fact that subway construction being done by private contractors was the reason for the metro + the station (overbuild by our standards) being 150M/km.
It is probably the same group of companies that builds most of the transit infrastructure in Toronto, Vancouver, and the rest of North America.
Many differences between Montreal and Toronto can contribute to construction cost differences:
1) Land quality/soil conditions
2) Building codes (Ontario's are likely stricter in the ways of fire safety)
3) Competition from private investment -- condo development is still rolling along sucking up huge resources. Pearson Airport rebuild caused a visible construction price increase across the city; these do too.
4) General wage, health and safety regulations, etc. Often the qualified companies (PCL, etc.) are the same in both provinces.
5) Materials pricing. Quebec isn't as picky about sources of things like aggregate.
6) Willingness to disturb locals during construction. Toronto often goes well out of its way to avoid closing streets which forces "just in time" delivery of materials and crews. Very significant communication overhead.
7) Advertised vs. actual budget. TTC will probably hit their numbers. Montreal has a bad habit of underestimating by a wide margin with the Laval metro expansion being a really good example (actual cost was 6 times the original budget; "only" doubling the price would be an improvement and in the same ballpark as TTC costs). Comparing costs after the fact is far more appropriate.
8) TTC includes (for the most part) storage, facilities, and rolling stock in its estimates. Montreal, to my experience in the past, has not.
9) Bidding process or transparency/fairness of government. Not surprisingly, the more controls in the bidding process the more work it becomes to bid and that pushes prices up. We seem to prefer spending $5 to monitor the process than risk losing $1 to questionable activities.
