During the rollout of Flexities, I did a study of turning speeds at Queens Quay and Bathurst, CLRV's averaged 15 km/h and Flexities averaged around 11 km/h. Based on interviews with operators, the slower speeds on Flexities were due to a combination of concerns about dewiring, and discomfort due to the jerky motion of the Flexities around corners (due to the awkward wheel arrangement). I haven't done another study since they switched to pantographs, but I suspect that it remains about the same, since the main limitation was discomfort.In fairness, just because they can, does not necessarily mean they should. High floors have a greater degree of flexibility because of the full swivelling motion of the trucks, but if a driver powers up midway through a turn, it makes for a massively uncomfortable ride even so.
I'm not sure how fast the TTC streetcars turn, but I'd be shocked if it's faster than 15 km/h. At the ride quality offered by Flexitys, I'd want a seatbelt!