Originally posted by Omega Vision
Well if memory serves DC referenced JLA/Avengers (which for DC at least is canon) and the Avengers in particular as the "others". No direct naming but that doesn't mean it didn't happen they just don't want to get into lawyer territory.
The funny thing is that JLA/Avengers was said to be canon for both companies though if Marvel would decide that it's not canon then it would be not canon for both.
Marvel vs DC isn't canon to both, it wasn't during it's release and it wasn't after it.
The Mxy thing is IMO something different, as those "FF" moments from the DC comics couldn't be considered canon til the moment Marvel made them canon with their Impossible Man's OHOTMU bio.
The fact that it was a canon DC Mxy-story and the fact that Marvel deemed it worthy enough to be mentioned in the bio does indeed make it canon. IMO. Though it comes as a surprise as i have never heard of anything similar. It's really unique.