If you include AM DX in your question, I regularly heard some Canadians when I was living in Portland several years ago. At night, Montreal's CKAC was a loud, consistent regular on 730. VOCM from St. John's, Newfoundland (don't recall the freq) was often heard after midnight.
When I lived on Peaks Island (a few miles offshore from downtown Portland), for some reason CJAD, Montreal on 800 came in surprisingly well late into the morning even in summertime, although I rarely heard it in the city of Portland itself.
It's not Northern New England, but in my hometown of Buffalo, NY at least 5 Toronto AMs are always nearly as loud as the local stations all day, all year. Since the late 70s, many Canadian FMs are also clearly heard in Buffalo around the clock. One of the them, CKEY-FM, licensed to Niagara Falls, Ontario if I'm not mistaken, even markets itself to a Buffalo audience. In the last arbitron, it had a 2.5 share, not bad for a cross-border rimshotter.
Nick Seneca