The transit authority did have an app, which they’ve pulled at some point (as far as I understand, they felt like they couldn’t compete with the level of transit info apps out there — which isn’t untrue). There’s also the Transit app [0] that is made in Montreal, so I guess that they (the transit authority) were happy to shine a light on that (pretty great) app.
In any case, one of the neat things about the Pi sign is that it works for everyone (whether you have a phone or not), and is part of the urban landscape. You can use your phone for more important things, or just leave it alone a few minutes while you wait. :)