Not sure about Bluray, but I was able to play 3D (side-by-side) movies from my ATV - via an old HDMI switch and an old AV receiver - no problem.
However, when playing 3D games on the 360, I had to bypass the HDMI switch and receiver so the HDMI went straight to the TV and the optical audio to the receiver; which made switching between the 360 and other devices more awkward (need to switch the AV receiver's input for the audio and the TV's input for the video).
I never actually tested 3D on the 360 when connected via the switch & receiver, but everything I read online said it wouldn't work unless both support 3D.