Just because its possible doesn't mean its practical. Yes Ottawa does run on Low Floor vehicles, but at a massive cost, that being future capacity. Simply put, by running on low floor vehicles, Ottawa now has less capacity in their trains for no apparent reason. As for the Sheppard Line, there is a good reason of using high floor, even in a median setting, which is the existing subway. Your two options are either A) Have 2 services running along Sheppard, a subway from Yonge to Don Mills, then an LRT from Don Mills out East which not only is it messy, but is extremely inconvenient for passengers travelling to North York Centre. Your other option is to modify the existing subway to LRT which if done using low floor technology, would require changing the height of the platforms which is expensive and frankly unnecessary. Given these scenerios, if we had to make Sheppard East an LRT, the best solution would be to run High Floor LRTs using the existing subway segment.