Lets determine the diagonal for a full-frame still camera like the Canon 5D. As you know the BMCC uses an aspect ratio of 16:9 for its image. So the diagonal for the full-frame camera with an aspect ratio of 16:9 is 41.3 (square root of 36*36+20.25*20.25).
The MFT has a diagonal of 21.6mm and a crop factor compared to a full-frame still camera like the Canon 5D of about 2 (41.3/21.6).
The BMCC EF and BMCC MFT both have identical active sensor dimensions for the image frame and that area has a diagonal of about 18.125 (the square root of 15.81*15.81+8.88*8.88) with a crop factor of about 2.278, lets call it 2.3 (41.3/18.125).
Some C-MOUNT LENSES have been tested for micro 4/3 that has 21.6mm diagonal..let's see what of these lens should be "usable" with Black Magic Camera.
Here is a rumor list...users should add or change info if they own and have tested lens...
This is an informal test..