The RAW bayered image size is 2432 x 1366 which gets debayered to 2400 x 1350. There is a slight crop to get rid of the edges of the image because when you are debayering, the very boundary of the frame will not have enough surrounding information to be accurately debayered and will need to be discarded. This is a pretty standard procedure for debayering images.
The DNG has a DefaultCropSize tag which is explained as:
Raw images often store extra pixels around the edges of the final image. These extra pixels help prevent interpolation artifacts near the edges of the final image. DefaultCropSize specifies the size of the final image area, in raw image coordinates (i.e., before the DefaultScale has been applied).
EDIT: ..the files are indeed 2432x1366..
i got proactive and have written a small tool that can process a folder of BMCC dngs at full res. (2432x1366), and extract the raw greyscale cfa etc , and do some other stuff