Film 3D is mostly Linux at this point. All the major VFX shops (like Weta) and animation studios (Disney, Pixar, etc) are on Linux for artist workstations. Apple stuff gets lots of use, but mainly iPads for story boarding and such.
> Pixar began in 1979 as the Graphics Group, part of the Lucasfilm computer division, before its spin-out as a corporation in 1986, with funding by Apple Inc. co-founder Steve Jobs, who became the majority shareholder.
"Steve wasn’t capable of being friends. That wasn’t his personality. Besides the Apple stuff, I had a lot to do with his Pixar thing. I was contacted by the people who became Pixar–I knew them well, and they wanted to get out of Lucasfilm. They called me up and asked me for advice, and so I said, I can talk to Steve. I explained very carefully to him who these people were, and you shouldn’t fuck around with them, like he did with his normal employees. He did a good job with them. [Pixar] was the most honest billion he ever made, because he put a lot of his own personal money into nurturing those guys. They got fabulous. That was Steve’s best hour."
Alan Kay - https://www.fastcompany.com/40435064/what-alan-kay-thinks-ab...
It is true that we have Mac systems here, that's no secret. But all 'real' film production work is completely Linux based with a completely custom infrastructure.
Source: Currently at Pixar
(Also almost every single one of those is from a CEO or VP, not someone who's job it is to actually use these things.)