thanks all for useful info.
At the moment seems we will go to Timboctou to see the music festival in mid-Jan, and then we will see in Gao, is it possible to get this transit visa, and what the locals will suggest about Borj Moktar route. If we will have no chance there, we will return through Mauritania again, hitting some other route then.
If anybody has some additional info about Borj Moktar, it will be greatly appreciated.
On other hand, may be somebody wants to join us - two couples squeesed in '91 Toyota 4 runner?