I have found a solution in 15.5 moves:
1. a4!? c6 2. Ra2 Qb6!? 3. f4 Qxg1 4. e3 Qxh2 5. g3 Qxd2+ 6. Bxd2 a5 7. Rxh7 e5 8.
Bxa5 Rxa5 9. Rxg7 Bb4+ 10. Nc3 b6 11. Rxf7 Kxf7! 12. Qxd7+ Kf6 13. Qxc8 Na6 14.
Qxg8 Rxg8 15. Kf2 Rg5 16. Bc4
I have written a WordPad document which together with a mess of variations (not sufficiently annotated for proof standard, though) show that this is indeed the minimum number of moves needed. I will publish the analysis when it actually comes close to a rigorous proof, but until then, you can take my word for 15.5 moves being the minimum.
See http://rybkaforum.net/cgi-bin/rybkaforu ... #pid557167
for more details on the problem.