When they built the underpass road, they built the concrete box that would support the Dufferin line going north of Queen and fill the hole in with asphalt. When time came to build the line, asphalt is remove and tracks place in the hole. the ends would be remove to allow track to continue in both direction. I have photos of this track protection in the centre lane, but for some reason most of the photos I shoot for the construction of the underpass are missing in my Flickr account. No idea what the time frame is for when I shot the track base.
My impression at the time, there would be no northbound switch work due to location. The Queen line would see a diamond added if the line surface.
The idea that was around at the time, was the Dufferin line would go to Dupont and loop there. Now if TTC had duel end cars, no need for expensive loop and having the line stop at Bloor.