No - the IPod does not present audio data through the USB interface.
The "wide" connector that attaches to the iPod itself *does* have audio, which is why the various third-party iPod docks work, but that signal doesn't end up on the USB section of the connector.
To do an audio pass-through, we'd have to add the full connector - however, that requires a license from Apple,which comes with some additional strings, as well as incurring the cost of the somewhat pricy connector and the license.
The only other way to do this requires substantial hardware hacking - removing the internal microphone and replacing it with an audio input jack, then writing some simple software to route microphone input to the speakers.