If the phone workd with Telus, Koodo, Bell, Virgin, Lucky, Rogers, Fido, or Chatr then it's compatible with Public Mobile.
If the phone works with Freedom or Wind then it's *probably* compatible.
The phone must be unlocked. And not blacklisted, not reported as lost/stolen, etc. Easiest way to test is to try it out with active SIM cards from at least two carriers - a carrier-locked device won't work on any other carrier. (You may not have extra SIM cards - to borrow for a few minutes from the phones of friends and family - but any cellphone vendor/kiosk agent certainly has lots of active SIM cards handy, you can go to two or three of them.)
If it's a used phone then you can use a battery checker app to report battery age and how many charge/discharge cycles are on it.
If you want a phone from Alibaba/etc which is primarily intended for foreign markets (China, Europe) then you'll have to research the phone specs and reviews carefully - there may be no version/model of the device which is fully compatible with Canadian networks - be certain you can return/refund a device which can't deliver as promised.
