To be blunt, I don't trust the TTC's estimates. And again, conditions on Eglinton are basically the exact same (if not even better for transit,) as the B-D was at the time of its construction. And would you argue that transit in the city would be better if the B-D was LRT past Keele and Pape? I really doubt so. There is such a thing as investing in your future.
Almost certainly provided the same amount of dollars was spent. Might have a Queen LRT tunnel through downtown in lieu of tunnelled BD past Pape and Keele.
We wouldn't be looking at congestion issues at Bloor-Yonge with that configuration. King, Dundas, and Queen trains (even Yonge had multi-car trains) could be converging on the tunnel to get through downtown quickly dramatically increasing capacity on all 3 lines.
There is no wrong decision with transit spending in Toronto; but some are more right than others.