Why do you assume this? I haven't heard about any addition like this, and if Nokia were going to add something like this I don't see why they'd wait until PR1.3 to do it. It is possible for T-Mobile to use a technique known as TCP fingerprinting where they analyse the characteristics of yout TCP/IP packets to guess at what OS you are using, they might also check your browser headers to see how your browser identifies itself, they might also look at the type of traffic and if it is traffic they wouldn't expect from the type of device they expect you to use they might block you based on that.