Is the BPAV on a hard drive and not the actual camera card? I had a similar issue with Canon 300 files on an external drive. The solution was to select import from camera, and then when the import browser launches (and you see no clips) select from Camera Archive on the bottom left). Then the clips come up and you are good to go.
So that might work.
Also, on a project using a Nano Flash with XDCAM, recording a 100MBPS, I had to use the Sony XDCAM converter to re-wrap the files first. But when they were coming of the camera card (at the 'normal' MBPS) they imported directly into X.
I don't know if these two illustrations help, but they do show that X is particular, but there is always a pretty easy work-around.