Ok, been doing a bit of research and made a couple phone calls. Still waiting on an e-mail, but I have enough info to pass on.
For anyone who wants to run aftermarket rims and tires that are different in size from the stock 14'' 185/60/14's, Your recommended inflation pressure may change as well. Proper pressure will improve ride quality, and make your tires last longer, as well as reduce risk of blow out.
Your TPMS is not locked into the recommended pressure for the stock rims. There is about 5 pounds free play in either direction (if I understood the dealer correctly.) This means when you do a learn procedure, the TPMS should accept pressure ranging from 26 to 36 LBS of pressure. I highly doubt the pressure in your tires will change by more than 1 or 2 LBS.
So, If you are willing to spend the money, TPMS sensors for your new rims not be wasted money.
If you want the TPMS range on your vehicle to be changed, you will have to Shop around for a GM shop that is willing to do this. According to a few other chevy forums that I browsed while looking this up, many dealers will say that they can not change these values. Others will do so at little to no cost. They will say they can not, and It might be true for our vehicles (I'm still researching this). The people who were able to get it changed owned 2500 and 3500 HD pick up's, I don't see the chevy systems changing that much, even with their foreign affiliates.
At the very least, you can run a TPMS on your aftermarket rim and tire, and still run the proper pressure for that tire, without the sensor being completely unreliable.