UPS and FedEx don't have a different special process for iPhones. A box with a shipping label that has an iPhone in it is treated the same way as a box with an identical shipping label that doesn't have an iPhone in it. If T-Mobile are really waiting until tomorrow or Thursday to start shipping out phones, UPS are just gonna pay attention to the shipping label and that's it. If it says ground shipping then that's exactly what they'll do, ship it via ground.
With that being said, I really do want to believe you because I want my phone on launch day... I just don't have much faith in T-Mobile now that they've already printed my ground shipping label.