One thing that I haven't seen mentioned - tho the phones will be untracreable, since there is no record of who bought them, tracking will be able to determine what cell phone a call comes from. People think that it's just the SIM that is operational in GSM phones and thus only the phone # is sent, but part of the DNA of the call is a serial number that identifies the actual phone itself.
A Brit lady found this out the hard way when she used her ex-hubbie's SIM to send threatening tm's to him - LE was able to bust her even though it looked like the tm's were coming from his number.
For some reason it must be easier to make cash-only, anonymous purchases of large quantities of these types of phones in the US than in Europe or the Middle East.
Looking at the Tracfone website, I don't see any reference to international roaming arrangements, so apparently you can't take their prepaid phones overseas and actually make a phone call. Furthermore, if these are the cheapest phones, then presumably they are not dual or triple band and would not work with a GSM network anyway.
So the explanation by the men described in the Dallas Morning Herald article that they were collecting the phones for a man in Dallas who was in turn reselling them overseas doesn't seem to hold water.