The Apple driver uses app automation to add and delete books to iTunes and modify metadata. The available APIs do not expose any functionality to do file IO with iOS apps other than iBooks. If anyone's interested, you can review the exposed functionality by opening AppleScript (on a Mac) and then opening the dictionary for iTunes.
So itimpi is correct, it's still not possible to talk to other iOS apps through the Apple device driver. At least I don't know how one would do it, and I haven't heard of any other apps doing it.