@256cell The mnc is 001-001, but this phone shows AT&T no matter what I do. It was originally an AT&T locked model, so maybe that has something to do with it? But all other phones I tested just show "Test" or show 001001, which is correct.
Just briefly coming back to Twitter to show the Cellular enthusiasts that follow me what I did: I am running my own GSM network, giving me access to calls, texts and GPRS data (no Edge data yet, but I'm working on it). Only needed $150 radio and an old Intel NUC to make it work!