Thanks x14, I just discovered that! It seems that as long as you activate on the 4.1 server it will come over. This doesn't solve the core issue but is very helpful... now I just have to get T-Mobile to give me a report correlating SIM ID's with phone numbers... we'll see how that goes.
BESX 4.1.7 on Exchange 2003: 65 Devices
BESX 5.0.3 on Exchange 2003: 2007 Devices