Yes any OS X Lion and Snow Leopard can run AU LAB. Apple’s free digital audio mixing application, AU Lab, can be used as a host application for Audio Unit effects, including AURoundTripAAC Audio Unit, one of the new Mastered for iTunes tools. If you don’t already have Logic or another Audio Unit host application, download AU Lab to get started with auditioning your audio, detecting peaks and clipping, and performing double-blind listening tests.http://www.apple.com/itunes/mastered-for-itunes/
Your concern in the main text that “running FB2K on WINE/Crossover or on a virtual machine [can be done in] very few easy ways” might be assuaged by reports from others who have found it to be easy.
Would you mind explaining, please step by step, how to set up an ABX test with this toolchain (and possibly save the resulting logs)?
[1) Download the Audio Mastering Tools
I've only tried it briefly and AFAIK it's only possible to ABX the apple codec, not two different audio files.
On top of that I couldn't find a way to get rid of the delay caused by the AAC coding, which makes the ABX easy and invalid, because the source is always the one without delay. If someone knows a way to compensate for the delay, please chime in.