Thread is nearly 2 years old...but OP, were you able to swap 'em? I was going to put aftermarket wheels on when I took my snows off today but I didn't see any way to move the sensor to the new wheels without at least replacing the stem. I have plenty of non-TPMS valve stems but I'm pretty sure the TPMS sensor needs to attach to a specialty stem...I guessing I'd be better off buying 4 of these: http://www.amazon.com/gp/product/B002DYB258 than buying the specialty stem from GM. The pic on Amazon looks like they are similar to Toyota OEM which are very easy to swap.

I ended mounting my summer tires on the original steel rims. I think I'm going to send the wheels back to tire rack; the centering ring was a little loose anyway.