Have we not learned from Ottawa? The conversion to LRT is a painful one. In our larger cities, we should avoid busways/transitways as much as possible. Build rail transit or don't waste the money. With so few transit dollars, we should only build on things that will bring the most benefit. Problem is, busways/transitways are a great political tool during an election.
There are three problems with the BRT in Ottawa:
1. It is the backbone of the entire system in the city of Ottawa.
2. Not only is it the backbone of the entire transit system, but the busiest, central portion of the route, Albert and Slater, is on-street rather than off the street and grade-separated. In other words, the busiest portion of the route has the lowest capacity.
3. It snows a lot in Ottawa, and articulated buses can't operate in snow.
An Etobicoke transitway would not act as the backbone of the TTC system. Even in Etobicoke, it would still be a secondary corridor compared to the two main corridors, Bloor and Eglinton. The Mississauga/Etobicoke/407 Transitway system as a whole would be a crosstown service rather than directly connecting to downtown as the Ottawa Transitway did. It would connect to lines connecting to downtown rather than connect to downtown by itself. Every station would be suburban. Even Kipling Station is suburban in nature.
And since the transitway would be entirely in suburban areas, it would easier to build an entire off-street, grade-separated system with bypass lanes at stations that can match LRT in terms of capacity (LRT lines typically do not have full grade-separation or quadruple-tracked stations).
The ridership of a BRT corridor in Etobicoke will very high but not enough to justify LRT. Ottawa Transitway had 240k weekday riders on it, around half of OC Transpo ridership, and more than all of the TTC buses in Etobicoke combined. It was just an exceptional case.