Although it has always been possible to mount an ENG style Servo Zoom Lens to a mirrorless system (with a bit of fiddling), FotoDiox is developing the PowerLynx complete adapter kit to make this mod easier and more affordable.
The PowerLynx adapter we tested at the show was a working mechanical adapter with some vignetting at the wide angle. One version (currently in production) will have correcting optics built in to the adapter to eliminate vignetting and should be available in 2-3 months. I'm looking forward to trying this out with my GH3, BMPCC, as well as the new #GH4 when it arrives.
For more information about Fotodiox adapters and other products, check out http://Fotodioxpro.com.
FotoDiox PowerLynx ENG Servo Zoom Lens Mount Adapter