The Queensway has varying widths. Widest west of Islington, it wouldn't be too difficult to get an LRT in from there to Sherway. East of Royal York to the Mimico Creek however would be difficult, likely resulting in multiple expropriations.
The tightest spot on the Queensway is east of Royal York, at 26 meters between buildings. St. Clair is 30 meters for comparison. It would be tight. Most of the queensway beyond what is essentially just 2 blocks east of Royal york is 30 or more though. it jumps out to 30 meters once you get to Penhurst.
What are the Queensway's traffic counts compared with St. Clair? What's the model split? Currently the Queensway bus would carry a pitiful fraction of what the St. Clair streetcar carries, and the Queensway would have more private vehicular traffic than St. Clair either before or after the separated ROW was established. The two streets are apples and oranges in terms of their mid-urban context and therefore the way they are used. Reducing traffic lanes on the Queensway to the same extent that was done on St. Clair would be much more problematic.
no traffic lanes were removed on St. Clair, they simply dropped parking lanes which in effect dropped an off peak lane as off peak the outer lane is used for parking. during peak times St. Clair theoretically still has the same amount of lanes. There is only around a 500 meter stretch on the Queensway that would have to drop the parallel parking, and by a quick street view look it looks like that stretch has more than enough off street parking already. Otherwise there is a fairly large grass median along the Queensway right now that could be eaten up by the wider road.
My only worry would be fitting 4 car lanes and 2 streetcar lanes through that 26 meter ROW.
Yes, the big problem on St. Clair is during off-peak hours when it becomes a one-lane road in each direction.
While I'm glad of what happened on St. Clair, it's wrong to believe that dropping that lane during most hours of the day was the only thing that happened to slow traffic. During all hours, the narrowing of the lanes and the increased channelization forces the vehicles to slow down to navigate the twists. Other than at the underpass between Keele and Old Weston Road it's an acceptable price to pay to improve transit.
On the Queensway the question is whether putting in an LRT would lure enough people on to transit. Currently there's a bus along that route once every 30 minutes at off peak and peak hours, which increases to once every 24 minutes between 9:30 AM and 3:30 PM. In other words, the modal split here is really, really bad. They simply could not justify the expense of building an LRT along here without attracting many times more riders to this bus route in the first place.