From a quick Google search, it appears that a Net 10 "SIM" card doesn't really work the same way as most SIM cards. It seems to be "reverse-locked".
That is to say, in a conventional SIM locking arrangement, the phone knows what network it "belongs to", and it will reject any SIM which was issued by any competing networks.
In a Net 10 SIM, the SIM card itself also knows the IMEI of the phone it was originally paired with, and it will reject any phone which reports a different IMEI.
http://reviews.ebay.com/TRACFONE-NET10-SIM-Card-Information_W0QQugidZ10000000001818964
You'd need to either hack the iPhone to report a different IMEI, or else figure out a way to modify the TurboSIM so that it relays fake information in both directions - a fake MNC/MCC to the iPhone to make it think it's on AT&T, and a fake IMEI to the SIM card to make it think it's inserted in its original paired phone.