Currently there are 50+ stations which already have WiFi service and many already work with Freedom Mobile/Wind. Tconnect has invited carriers to sign onto it's network but so far only Freedom Mobile/Wind has.
Connecting to the WiFi hot spots is too slow when you're in a moving subway and once you're connected you get disconnected very quickly. Often so quickly that there isn't enough time for a smartphone to even sync it's emails, notifications, etc. Especially when going through the sign in page.