If that 2006 incident resulted in the elimination of all escalators at Union it looks like the typical Toronto/Ontario over-reaction (often with a less than satisfactory replacement). The Yonge Street van attack resulted in Jersey barriers @ Union; MAYBE acceptable as a temporary solution but not one that should still be there. MANY places seem to manage to combine escalators and crowds (New York and London UK anyone?); the old Union escalators may have been too small, too few or too old; but after 16 years I think proper replacements could be found!
Though honestly they need to figure out exactly what the platform arrangement will be before installing escalators - can you imagine them doing it the way they have messed with the station the past 2 decades? That would be putting the cart before the horse.
The reason they were eliminated was because of an accident in the station during rush hour.
Too many trains let out at once leading to a pileup at the bottom of an escalator due to overcrowding.
There was one that remained on Platform 25 but only went up and not down.
Geez trains and bus accidents happens - so let's not run trains and buses at all! That seem to be the default mentality of some organizations - less about serving the public and more about minimizing liability.