Well, the Torontist picked up my story, and did a little investigating of their own with TTC customer service. It turns out they really were taken down due to public safety concerns, which I call shenanigans on.
Anyway, the Torontoist post got a lot of comments, mainly supporting the signs, so I decided to start a little petition to save the signs.
Is walking up the escalator really unsafe? If someone shows me good data that it is, I'll gladly stop the campaign.