The Eglinton tunnels are being built to subway specs. So strictly speaking, there isn't a need for a new EA.
Correct me if I'm wrong, but I recall reading somewhere that due to the smaller dimension of LRT vehicles, the designers opted to use one larger diameter tunnel two tracks wide as opposed to two separate smaller tunnels or a box cut with columns down the middle. Because of the larger size of subway vehicles, two parallel subway trains could not fit in the same space as two parallel LRT vehicles, thus the Eglinton tunnels cannot fit existing subway vehicles.
I have conceded that an LRT based Eglinton line is ok, provided that:
1) The tunnels are signaled so that the operation of the vehicles is not up to the drivers' whim.
2) Gap trains are consistently made available for underground portions to maintain frequency, in case surface vehicles are tied up by weather or traffic lights.
3) The portals are designed such that extension of the main line underground would be easy enough in the future to not be a deal breaker.
4) Fares are paid to enter the station, not to the driver.
5) Platforms are raised to the level of the doors, and sufficiently long to accommodate full length trains in the future.
If the underground portion will be identical in nature to the underground section of the Harbourfront line, especially Queen's Quay station, it will be just dreadful.