Prospects for getting an assitantship | How do professors hire in Canada? I have applied to one of the top engineering school in Canada: UoT, University of British Columbia &amp; UWaterloo.

I've interviewed a professor and he sent me his most recent research publications after the email. I asked a few prospects of the future project he wants me to work on and he even encouraged me that we can think of using a methodology (that I previously worked on) in his future project. 

He's told me he's reviewing all the people who opted for his research supervision. More info in this thread 1.

So, what kind of chances are there for getting a Master's assitantship based on the professor's response? Do all professors have this enthusiasm while discussing with prospective students? 

I apologise for this very specific question but anxiety kicks in during the admission process :)
First of all, the notion of " top engineering school in Canada " only makes sense in the academic bubble. I did my B.Eng., M.Sc.A. and PhD in a lesser-known French-speaking university in Montreal (École de technologie supérieure) and I work with people from Stanford, MIT, UBC, UWaterloo, etc. I did go to UBC for an international internship program during my bachelor's degree and it has many things going for it including the magnificent scenery, but I didn't go there for my postgraduate studies even if it does have an excellent reputation and better name recognition. All this to say that, in my opinion, you shouldn't put more pressure on yourself because it's UBC or any other brand. Amazing research is being done in places you've never heard of. You could lessen your burden by de-narrowing your scope.

To answer your question directly, to my knowledge, it is common for professors to share their research enthusiastically with prospective students regardless of if they think they'll hire them or not. There are too many unquantifiable variables to ascribe any sort of value to the chance of getting the assistantship you're seeking. What I can tell you is that professors are starving for competent students. If you're competent relative to your peers, you can bet you have more than a coin flip's chance of getting it. This is as close to an actual measure as I think you can get.