You can add a handler to cancel buttons just fine.
Assuming your cancel button is called "cancelButton1", you can go to the page in the client, open the console and paste this:
require(["dojo/on"], function(dojoOn) {
dojoOn(document.querySelector(".mx-name-cancelButton1"), "click", function(e) {
console.info(e);
});
});
You'll see that the listener is executed correctly.