Any day now, if it's not already in place, a trial is being conducted by CATSA at Pearson airport with the use of NEXUS cards. As you know, NEXUS is a form of screening, because it involves a background check, a review, whether there was any criminal activity, etc. It tends to reduce the size of the haystack so that you can find the needle.
Now, those people who do have NEXUS don't go off scot-free. They are subject to a certain amount of screening, but they aren't necessarily subject to pat-downs, etc., and they are able to move through a queue faster.