I asked Customer Support this question ealy this month. The reaction I got was:
We have to inform you that BeoMaster 5 is not specified to work with Apple Lossless
formats, and therefore cannot play such files.
However, this is something which is being looked at, but no definite plans have been
agreed upon yet.
We have passed your wish on to the responsible department for their information.
Perhaps I am a bit cynical, but I do not expect much taken into consideration the last software updates. However, you never know :-)