Is it possible to use the new Rock Band 3 instruments cross-console?

If I have the Wii version of the peripherals, is it possible to use them with my Xbox 360?

The reason I think this would be possible is because they are midi-capable instruments that can be plugged into my computer and work fine there, and they communicate to the Wii using a USB dongle. Since the Xbox has USB ports as well, it is physically possible to connect them to my Xbox without any further modifications.

Will they actually work to play the game, however?

Is there some way I can make them work if it's not just as simple as plug and play? I am willing to spend money on a third-party peripheral to "translate" if necessary for this functionality.

No. Despite the fact that all 3 consoles use USB as the connection protocol for the instruments, the actual signals sent and button layouts of the controllers mean that none of the controllers can be used on other platforms.

No. All 3 major consoles use different interfaces and wireless standards to get their controllers talk to the main box.

I am sure that the stores would love nothing more than not having to carry 3 different SKUs for essentially the same (bulky for gaming) item.