AT&T Adds Wi-Fi Support to Its Enhanced PTT Service

I'm wondering if AT&T's EPTT over local WiFi is a secure means of communication. Nextel's iDEN-based PTT was considered to be fairly secure (i.e. not easy at all for others to listen in on conversations), and that was a huge selling point to both private companies and law enforcement users. Does anyone know if AT&T's EPTT is equally as secure when it switches over from AT&T's main networks to a local WiFi spot?

BTW Phonescoop, what about having a head-to-head comparison of PTT performance & features from Sprint, AT&T and Verizon, with Nextel as the baseline to compare all three of the newbies to? Including when an AT&T EPTT customer has no LTE signal and it drops back to 3G signal, same for Sprint & Verizon, how does each perform when in an optimal network location, and how does each PTT offering perform when on the worst parts of each of their networks. If you can pull off such a test, don't wait too long because soon you won't have anyplace you can do the Nextel baseline ;-)