The dealer can't disable it, by law. Physically, they can. If they disable it they are violating a federal law that states you can't disable federally mandated safety devices.
Crock of BS if you ask me. I use a TPMS system that only costs about $2 - look at the tires and see if they're low. Or, use a gauge to take the pressure if they do look low.
2011 Focus SE 5 Speed.