Where to begin?
To start, the whole cut vs. ground beef debate. Whole cuts have just as much a chance of being contaminated as ground beef. It's just that the cooking process kills most any bacteria on the exterior and (as Ed pointed out) the interior is safe. In ground beef, the grinding introduces the bacteria on the exterior to the interior so it is pervasive throughout. BSE is not believed to be transmitted through a bacteria per se, though.
The reason for this recall is the use of downer (unable to stand) cattle. One of the signs of BSE is the inability of the animal to stand, so it's a risk to introduce them into the food chain. As far as how BSE is transmitted, it is believed to be through the ingestion of a malformed protein called a prion from an infected animal. These prions can found in the brain and spinal cord of such an animal. Any risk (and from what I've read, it's negligible) coming from meat on-the-bone is more than likely to come from on-the-bone cuts near the spinal column. These would include a bone-in ribeye, bone-in striploin steak, bone-in tenderloin and porterhouse/t-bones.
As far as tenderloin and bones are concerned, I'd say this picture pretty much tells you it does contact bone:

The tenderloin portion of this abuts the spinal column; the groove you see in the cross of the "T" is where the spinal cord was.