@Steve Munro 's latest post on a topic that's been discussed here. He spoke with the Metrolinx team:
In a recent article Metrolinx Plans Major Grade Change on Lakeshore East Corridor I noted that a new set of drawings had appeared in the Ontario Line Neighbourhood Update, East web page showin…stevemunro.ca
Further to new info being gleaned here.............:
That's a considerable added cost in scope that was not in the original proposal.
As to the idea of the Dundas Car to Gerrard Station.....from a POV of meeting the needs of riders of that route, the benefit is probably low; the benefit for the TTC is alleviating overcrowding at Broadview Station.
I expect that there has been at least some, back-of-the envelope consideration to how Broadview would function with yet another route (Broadview extension demands its own streetcar route); and a possible connection to service on Cherry.
I've talked w/some knowledgeable people and the general consensus is that 'fixing' Broadview would not be cheap. It wouldn't be Bloor-Yonge expensive, but it could well involve partial reconstruction of the station.
Shifting Dundas to a new routing might represent a cost savings by reducing the scale of such work, deferring such work, or possibly eliminating it all together.
Of note, there is a trunk sewer under Carlaw and that might impact on construction of new track work.
I think any connection via Carlaw would all but ensure connecting track to Queen were also built for redundancy.