Justice League vs. The Fatal Five and Batman & Harley Quinn have both been deemed canon by Bruce Timm, and by it's references to the previous serieses.
There is a lot of DCAU content, including comics, games, toys and tie-ins. From the start, Bruce Timm said they were not canon, so that's what we based this policy on. We might have articles covering them briefly, but do not consider the content for character history pages.
But THEY are considered canon by Bruce Timm and mentioning of events of the previous DCAU canon, even as far as going to reference that one line in Batman Beyond Return of The Joker of the new Arkham building