I'm going to take a stab at this. Are you looking to watch blu ray movies using your MAC + Tranquility DAC, or to do something else?
If you're using it as an external data storage device, I don't think it will be any different from using any other kind (i.e. hard disk / DVD / flash / etc). Data is data.
If what you want is to watch blu ray movies, I don't think this is a hardware issue as much of a software one. With macs many people often used external blu ray drives and then software to rip a blu ray movie to their hard drive into their favored format, then use their preferred media player to play back that file. Alternatively I've seen a number of programs out now that are blu ray movie players for mac, though these sometimes need an internet connection to deal w/ decryption issues.
In any case, using your tranquility DAC would be two channel stereo only. If you want multi channel, presumably you would have to use the HDMI or optical out to a receiver that can decode multi-channel - AND the player software would have to be able to output the multichannel sound format.
So - to make a long story short - if you're going to use it just as any other external data storage device - or rip blu ray movies to your HD - there no reason to believe anything should be different or work differently than it does now. If you want to watch that blu ray movie + output the sound (2 channel) to your DAC, you will need to get the appropriate MAC blu ray player software.
