USB can "piggyback." Look at any iMac. Ok, so don't do it on purpose, but if you happen to catch one out of corner of your eye, note that the mouse plugs into the keyboard, and so can other devices. There's a hard limit on USB 1.0, but each device get's it's own "signature" at initialization.
So, theoretically, if T-X did it right, both would work.
However, no MS game would have more than four controllers of any type functional at the same time, and mostly the xbox linux programs are what you'd want a keyboard and/or mouse for. Like web surfing, or entering commands, instead of hunting through an onscreen keyboard.
Other than that, you might still be able to use it at the same time for a memory card save, and maybe eventually a USB hard drive, but they're usually slow and internal drives are so cheap why bother?