"Disney uses a mix of Hyperion and RenderMan, as Hyperion is not useable for test renders, as it can take up to 15 minutes until a pixel will appear on the screen, as they trace millions of rays at the same time."

None of the things you claim in this sentence are true. Disney does not use PRman at all anymore.

Sorry, I guess what I meant was that Hyperion is perfectly capable of being used in test renders. The amount of time before you see any resolved pixels is of course dependent on the size of your scene, the desired resolution, etc. It could take 15 minutes before a pixel shows up, but that's not a standard case for production test renders in an artist's daily work.