I happen to think that the poor SRT has been unfairly treated as a whipping child in the past---which, by Toronto transit activist standards, makes me a total deep-tongue lover of the thing---but in light of the circumstances Toronto is in even I think the business case for preserving or extending it is very weak.
Subway dreams from the above posters notwithstanding, conversion to LRT is going to happen. Robert Pritchard will not come galloping in on a white horse pledging to build a subway.
1. It's a third system type, which means we need a maintenance department, spare parts, and a car house for vehicles which will run on only one line. If it is LRT or subway, we can use the same vehicles the rest of the city uses, with interchangeable parts, vehicles, and car houses.
This. Transit boosters often get very adept at crunching rough x-million-per-km numbers but forget what a significant capital investment yard and maintenance facilities are, and what kind of constant operating costs are incurred by not having interchangeable parts and needing to train maintenance personnel on different systems.
Even if the line isn't extended an inch, keeping the SRT as a linear-induction light metro will necessitate a major expansion of the yard facilities, . Add to that the continuing costs of keeping a workforce fully trained to maintain the things.
2. if Bombardier decides they don't want to make compatible trains again, we're screwed. How many times does this have to happen before we learn?
In light of how linear-induction transit systems have been sprouting up in Asia lately and how Vancouver is committed to sticking with Bombardier ALRT technology for its next three expansions to the SkyTrain network, I think the likelihood of the technology getting totally orphaned is slim.
Had the SRT been converted to Mark II cars ten years ago, we probably wouldn't be having this conversation, as there are enough Mark II-using networks that I can't see access to compatible parts and so on as a long-term problem. Indeed, if the SRT had been a bigger line with a bigger fleet, it would probably have remained in Bombardier's interests to continue to support the Mark I trains.