The 15% neutral AH cut has been the same since classic. The only thing that's changed was the deposit when they upped the min/max durations (which doesn't matter, since you get that back 100% if the auction sells.)
I did Horde -> Alliance a few months before BC came out, and instead of taking the 15% cut I just bought a bunch of lava/fiery cores, righteous orbs, arcane crystals/arcanite, etc and resold them. I ended up making about 10% profit off it too. As someone stated, just list the item for the min duration with 1c buyout and have both characters standing at the AH to buy it out the second you list it.