I just re-read your original post. Here is my advice and 0.02.
Since you already have a backup camera to install then take the other posters' advice and get an aftermarket solution. I don't see any huge advantage of using the BMW parts with an aftermarket camera. I'm sure the end result will be fine.
Having said that, I agree with rip222, I've heard good things about the E53 X5 backup camera. It's the E70 X5 backup camera that everyone complains about and that is a completely different animal.
If you do like the appearance of the Mini camera that you posted as a link then I suggest you buy the OE BMW camera kit and scrap the aftermarket camera. That is what rip222 did. See the link:
http://www.xoutpost.com/articles/x5/e...amera-kit.html
The design of the camera has actually been updated to look like the one for the Mini (see the small posted drawing; it is the handle strip with the integrated camera; so you end up replacing the entire handle strip with this mod and it insures that the camera is pointed properly) and no longer looks like the one posted on that link (see the large photo of an actual camera), but I believe all the rest of the displayed parts are the same. You can buy it from the ebay seller roveractive. Yes it's more expensive, but you'll have an OE part with a super-clean install that will look and work great.
http://cgi.ebay.com/ebaymotors/BMW-G...fAudioQ5fVideo