Yup I tried it. Fyi, I updated my phone to tmo ICS thru OTA. Maybe they locked it so we can't delete it? Because on my list, it shows a lock.
However I was able to add the new APN and got tether to work, but can't delete the original settings.
Sent from my HTC Sensation 4G using XDA
Device: TMOUS Samsung Galazy S3
Kernel: Stock @ 1.51GHz
Device: TMOUS HTC Sensation 4G (RETIRED)
ROM: Elegancia Blitz 2.7.0
Kernel: SebastianFM v1.5.2