And no, you can't use AT&T, Verizon and MetroPCS LTE devices on each others' networks, as the companies spec out their radios to exclude each others' frequencies.
Well that's also because nobody's doing voice over LTE, and they're still relying on the legacy network for voice (and fallback data service where LTE isn't available).
Every device sold right now is this hybrid of CDMA/LTE or GSM/LTE, so even if some AT&T device did support Verizon's share of the 700Mhz band on the LTE side, you'd not be able to talk on it on Verizon anyway.
At some point the network will be all-LTE (Verizon's said in the next couple years) and they can drop the legacy hardware. But in the meantime the phones just have an extra bolted-on radio that does a great job at two things: it pulls down data super fast, and it drains the battery just as quick too.
Well that's also because nobody's doing voice over LTE, and they're still relying on the legacy network for voice (and fallback data service where LTE isn't available).
Every device sold right now is this hybrid of CDMA/LTE or GSM/LTE, so even if some AT&T device did support Verizon's share of the 700Mhz band on the LTE side, you'd not be able to talk on it on Verizon anyway.
At some point the network will be all-LTE (Verizon's said in the next couple years) and they can drop the legacy hardware. But in the meantime the phones just have an extra bolted-on radio that does a great job at two things: it pulls down data super fast, and it drains the battery just as quick too.