Yes, my dogs often listen without treats. More difficult situations sometimes still needs treats but even then I try to not default to treats. More difficult situations would typically involve other dogs in the environment and my dogs not being able to focus on me but I have to say that lately, simply saying 'leave it' and saying it rather 'meaningfully' seems to work. I look for those subtle hints that the dog(s) heard me and I praise in a happy tone.
Hey...would you come anywhere in Canada, maybe when you get your 25,000 hits!..I can draw you a map of where I live:))