My accounts are still with Lucky Mobile, they still have unlimited data cap. The way that works is that you get X amount of data at 3Mbps (Public Mobile's and Lucky's full speed). Once you pass that X amount of data, you still have the ability to use the Internet, but at a greatly reduced speed.
Before reducing the speed, videos are no problem.
After reducing the speed, you're looking at e-mail, messaging and facebook being usable. Youtube, not really.
It's the same concept that Telus, Bell and Rogers use on their plans.
If Public offered the same, I'd consider coming back.