Greg Howe has posted the following update on his site:
"UPDATE: Due to pending litigation matters, the Introspection Backing Tracks will be temporarily unavailable for digital downloads. CD version of the backing tracks, at this time, are available with the purchase of the Introspection Tablature Book. However, they are available only with the purchase of the book and are currently not being sold separately.
As this matter is subject to change, we will be sure to keep everyone posted with any new information."
I found the backing tracks have in fact been pulled from iTunes, but for the time being they are still available for download via Amazon. Stay tuned for updates...