Fotodiox today has officially announced the availability of their B4 Magic Lens Adapter for BlackMagic Pocket Cinema Cameras. This adapter allows you to add a B4 Mount ENG Powered Zoom Lens to the Pocket Cinema Camera.
Keep in mind these lenses come in a variety of different types and brands, and in USED condition - so the results can greatly vary. The old B4 ENG lenses often found for about $100 dollars are originally designed for SD video, so I wouldn't get my hopes up on trying to achieve super sharp HD Video results. A powered zoom lens is just a handy tool, but maybe just for a niche market. In any case, you can find more information about this adapter over at the website (Found Here).
FotoDiox B4 ENG Powered Servo Zoom Lens Mount Adapter