I don't know about the Transporter, but my recollection is that the SqueezeBox plays 88.2kHz sample rate files by throwing out every other sample. Thus, while it plays them, it certainly doesn't "handle" an 88.2 file as an 88.2 file. It also does not output 88.2kHz.

This may be why the SB specs state only 44.1kHz and 48kHz, and the Transporter is 44.1kHz, 48kHz, and 96kHz.

Interesting question.