I have done 100+ domestic Canadian flights this year and have flown into and out of every major airport in that time. My experience in the US is much more limited, but I did come out of SFO just yesterday so I have some ability to compare.

Airports like YEG, YVR, YYZ all have the WBI machines, but I rarely have seen them in use on domestic flights. I think I've seen a total of 1 person being pulled aside in YEG for additional screening in my 30+ flights out of that airport this year. I've not seen them used in YVR, YYZ or YYC yet.

YHZ seems to be the exception. At the end of the security line they have the Dance-Dance-Revolution randomizer pad that points left or right. If you get right you go for additional screening. I've stood in line and tried to figure out the pattern and frequency and it does seem truly random in pattern, but the frequency works out to about 1 person selected for every 5 or 6 that go through. If you draw the lucky right arrow the CATSA employee says "Sir you've been selected for additional screening, please go to line 1."

I've been selected a number of times and once you're through the metal detector you are greeted with "Hi, you've been selected for additional screening and you have 2 options...." They carry on explaining the machine option and the opt out procedure. I have never not heard them make this explanation to me or the other travelers that have been selected. That alone is completely different than my SFO experience yesterday where I was just waved towards the WBI and had to stop and tell them that I wished to opt out.

I always take the opt out and without fail the procedures seems to be that the CATSA employee running the machine will raise his/her hand to get the attention of someone to send over someone to administer the pat down. This is unlike the TSO in SFO who yelled at the top of his lungs (complete with his hands cupped to amplify) "Male Opt-out Lane 1!"

Like the TSO who patted me down in SFO, the CATSA agents always ask me to explain why I chose to opt out. I've actually had some engaging conversations with them at this point. The one guy I have had pat me down a couple of times in YHZ has even gone so far as to say "If we wouldn't catch it with a pat down, the machine wouldn't catch it either so anyone who tells you they're better for security doesn't know much."

Overall, the demeanor of CATSA employees seems to be less abrasive, less condescending and more professional. That said there always are bad apples and I had one in YEG that had no idea how to read the x-ray screen and wouldn't back down on her assessment even after we completely emptied my laptop bag and didn't find what she claimed was in it (a lighter).