AT&T and Verizon plan to make cross-carrier VoLTE calls possible between their two networks. Is anyone really surprised by this when you think about it? One, it would be asinine to not make this possible considering that people need to be able to connect to others regardless of which carrier they are on. This is especially important considering that both networks see a future where all calls are VoLTE. Two, since VoLTE will use your data line instead of a cellular network it will eventually allow either carrier to charge overage fees for data phone calls. Regardless of the reasons for doing it, the two companies are working it out.
Here's a quote from Verizon's press release,
“Customers use their smartphones to connect with friends, family and colleagues across service providers and around the world. Interoperability among all VoLTE providers takes connectivity to the next level with HD quality voice and additional features that customers want,” said Tony Melone, chief technology officer at Verizon. “We’re pleased to be working with AT&T as our first interoperating carrier, and we look forward to working with other operators as VoLTE continues to grow.”
“Interoperability of VoLTE between wireless carriers is crucial to a positive customer experience,” said Krish Prabhu, president, AT&T Labs and Chief Technology Officer, AT&T. “Customers expect to be able to connect anywhere, anytime– and as LTE technology continues to evolve, it’s imperative that we provide a seamless experience between carriers. We are pleased to work with Verizon on this initiative. We continue to work with others in the industry on similar collaborative arrangements and hope to see similar collaboration across the industry in the near future.”
Source: Verizon