Advancements in push-to-talk-over-cellular (PoC) services have evolved to a point where they represent a threat to private land-mobile-radio (LMR) networks, potentially resulting in the construction of new LMR networks dwindling noticeably during the next five years, two speakers said during a recent webinar about PoC offerings.  “We’re talking about an enhanced push-to-talk system that is not mama’s push-to-talk system that Nextel had,” Steve Graves, chief information officer (CIO) for the city of Richardson, Texas, said during the webinar sponsored by AT&T (click here to access the archived session for free). “This is a push-to-talk system that actually connects to a trunked radio system. We’re doing it in Richardson. PTT-over-cellular improvements could impact new private LMR network builds within five years, speakers say