The short answer is yes, you can bring an unlocked phone.
Check out this site: http://willmyphonework.net/
You can input the phone manufacturer, model, then network (Canada>Koodo).
If the phone is really old and designed for the GSM network, you'll get no signal (old non-smart phones). For smartphones, you'll most likely get 3G. If it's a newer phone that's compatible with LTE with any of the big three incubents (Rogers/Bell/Telus), then you should even get LTE on Koodo's network.