I know the iPad will recognize and import (and export to LR) PhaseOne files that use the .tif extension, but not if the camera is set to use the .IIQ extension. You can see a thumbnail when importing, but since the iOS doesn't support Phase raw files you can't see images in the photo application. PhaseOne does create the typical DCIM folder structure. I believe I have read some other posts which imply the DCIM folder seems to be a required structure for the iPad. I haven't tested it directly yet (plan to sometime soon).
So if the Leaf back doesn't create the DCIM folder by default, can you use the back to "create" a folder?