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The thing with changing Eglinton to a full metro is that the plans and orders have been made for low floor trains with overhead wires. You would have to cancel and change the order, plus change the design of the line to support high floor metro trains. Not to mention, if it is to be integrated into the Scarborough RT metro trains can't handle the tight turns on the line.
I will agree that Transit City was second class, but LRT is far from that in reality. Here is a thread of examples of what LRT would be like on Eglinton East, if done properly:
http://urbantoronto.ca/forum/showthread.php/12557-Videos-of-Light-Rail-RAPID-Transit. I'm thinking that even if Eglinton is brought back from the underground, it will keep the underground stop spacing to provide true rapid service.