Seems like an usual replacement plan on the face of it, they must be predicting a decent growth in passenger numbers on the VLM routes as they'd be moving from a 58 seat F50 aircraft to a 78 seat Q400. Multiply this across the fleet and that's quite a ramp up in ASK's.
The C-Series is an interesting aircraft but will PW be able to deliver the engine on time? The last couple of PW projects have been expensive disaters (e.g. PW6000, PW4098 etc.). The latest CRJ1000 while being a relatively simple stretch has now been delay by about a year. Also, from my perspective, the E-Jets (e.g. E190) look like a better proposition in terms of getting your hands on a proven aircraft with most of the serious bugs worked out already.
Either way, all the best to them!