metadata - Can face detection information be extracted from the EXIF data on a Canon SX30?

I have been using an SX30 and they have a particular feature where each face has a bounding box when reviewing images taken with auto-focus set to Face Detect. There are two types of boxes: white ones, which indicate the face was being auto-focused; and gray ones, which mean a face was detected but not focused on.

My question is this: Is there some EXIF data that can tell me where the gray boxes are located in the image? I can find EXIF tags for the white boxes (based off of the AF points), but none for the faces that were not focused.