Actually, I contacted Logitech's corporate tech support and received the following somewhat non-precise answer about Apple's plus songs.

"Regarding your question, the Squeezebox or Duet will play music files in the following audio formats:

"Formats natively supported by the Squeezebox include MP3, FLAC, WAV/AIFF, and WMA (CBR & VBR). There's also non-native support for AAC (M4A, not M4P), Apple Lossless, WMA lossless, Ogg Vorbis, plus other obscure formats like MusePack and Monkey's Audio.

"As long as these files do not have the DRM attachment, the Squeezebox or Duet will play them.

As you will note there is not a specific answer, unless Apple plus songs are encoded as M4A. Thats why I hoped someone on this forum might know the answer.