Only until Bathurst, after that it cuts north, and bisects 4 major streetcar lines, giving the potential for transfers from the streetcars onto the subway.
But it doesn't replace any streetcars. It leaves them all in mixed traffic, competes with them stealing away their passengers, and leading to lower service frequencies on those routes.
There isn't much room along the north side of Queen either (Osgoode Hall, City Hall, Old City Hall, Eaton Centre). The only E-W street with development potential along it that is closer to Queen than to Wellington is Richmond. And even then, a mere 40 metres or so.
There are the properties on Richmond, the bus terminal, the club district, the whole area around Queen and Jarvis.
Why would you go to Jane? Tunnelling all that extra distance for what? You're passing south of High Park for most of it. You'd be overlapping the Waterfront West LRT on top of it. Dundas West makes far more sense, especially given the tentative plans to extend the Jane LRT south to Lakeshore.
I would eliminate the Queen streetcar, split the Waterfront West LRT from the Lakeshore West LRT with Waterfront West running Union to Roncesvalles, and Lakeshore West running Port Credit to Windermere. No duplication of services at all. I'm putting no stops under High Park. By going to Jane it connects with the Jane LRT. Jane south of Eglinton is too narrow and would require tunnelling and so would Pape on the Don Mills LRT line so it might as well form part of the DRL.
The way to fix the problem is to reduce the number of people that use it by offering more attractive alternatives.
Your plan makes existing services less attractive, duplicates service, eliminates nothing.
With the Metrolinx plan there will be frequent non-stop trains from Exhibition, Bloor, Danforth, and Kennedy to Union. It is cheaper to make the fare 2.75 on those and allow TTC transfers than it is to build a subway. With all GO lines going to Union, the Yonge-University line going south to Union, and the Waterfront LRTs going to Union.... who is out there thinking "I wish there was a way to get to Union".
With GO maxing out Union with its plans, the University Line being extended to Vaughan and new westerly LRTs dumping riders onto the University Line, and the Yonge Line being maxed out... the point of a DRL is to
serve downtown and to require as few trips possible to need to transfer to the Yonge-University subway. The way to require as few transfers as possible is to place the line in the middle of where people are going downtown (Chinatown, Queen West, Eaton Centre, Central Business District, etc.). A subway on Queen makes the whole area from Dundas to King walkable and therefore people don't need a transfer. If connectivity to the waterfront is required then we should extend the Bay tunnel from the waterfront up Bay to Queen.
Union has adequate service. Spend money to service places that don't.