I worked at two movie studios (Pixar, Weta Digital) and they were both almost 100% Linux with a smattering of Windows machines here and there. Apple stuff was mainly iPads for story boarding and that kind of stuff.
This is more for other readers as I'm sure you know this, but VFX / animation facilities are very different than other post-production functions like editing and sound, which almost always run on Macs. Final Cut and Logic are mostly the reasons for that (Blackmagic is making a real effort to change that though).
Well you forgot about ProTools which although I really dislike is even more important than Logic in post production. And Avid / Adobe on the video side. All of which will run on Windows and I am seeing increasing adoption of Windows in these places.