The film backs for the autofocus cameras are self contained insofar as the entire film transport gearing and motor are internally within them, but they rely on electronic contacts with the body for being instructed to wind on. And there's no way to wind them on by some external mechanical means.
Here's a way you can get around it.
Load a film, mount the film back on any AF body, and get it to advance to the 1st frame; then replace the darkslide, mount the back on your Arca, pull the darkslide*, make an exposure, replace the darkslide; mount it on the AF body again, pull the darkslide, make a dummy "1st" exposure (1/4000 sec exposure at f/22 with the lens cap on) so that it winds on to the 2nd frame, replace the darkslide; mount it on your Arca again...and keep repeating.
If that sounds too much of a PITA, remember, it isn't all that different to the complex sequence of steps when composing and shooting a view camera with sheet film!
Ray
* There's an interlock pin at the lower corner of the Mamiya back, to the right of the contacts strip, which must be depressed by the Arca camera mating surface - otherwise the dark slide can't be inserted or removed.
