I came up with this work-around to copy iPad / GarageBand audio files into my PC (Mixcraft 6) doing this:
1. Record your song using MIDI or Audio.
2. "Merge" each individual MIDI track, which will create an audio version
3. Close/Save the song
4. On iPad, click Edit / Share / iTunes
5. Connect iPad to PC, open iTunes, click on Devices / iPad / Apps / GarageBand
6. Select the song (it will be a folder), and at the bottom of the screen click "Save to..." and save the folder to the Desktop or wherever.
7. Locate folder on the PC, open it and then open the "Media" folder.
8. All the audio files will be there in the .aif format. The file names will be the original GB names; rename them if you like. The converted MIDI tracks will be labeled "Merged Track (1,2,3, etc)." Play the tracks to identify what instruments are on those tracks, and rename them.
9. Copy each track and paste it to an open audio track in Mixcraft 6.
This will probably work with any recording program that supports .aif files.
YMMV, good luck, it's working for me!