This isn't a news flash or anything... just back when this happened I didn't have a blog to point it out. And I do think it's somewhat related to our overall discussion of similarity, inspiration, etc.
Not that I mind one bit... I think it's great that 37signals is using a similar design for new post notifications in Basecamp. Yes, Beast had this first. I'm more than happy to lend them a few UI goodies from time to time - or even an entire forum. :-) Referring of course to 37signals switching to Beast (written by myself and Rick Olson) for their customer support forums.