These setups consist of a Nokia Mini Macro 2.5 eNB pole mounted on a macro site connected to sector antennas. Each mini macro is capable of up to 40 MHz of total LTE spectrum for 20+20 B41 carrier aggregation and are now being utilized to bring 2.5 on air if 8T8R equipment is unavailable or does not make monetary sense.
Nokia Mini Macro 2.5 Triband Antenna on Ericsson NV Macro (note decaport triband antenna & Nokia Mini Macro)
Nokia Mini Macro 2.5 on Ericsson NV Macro
(note 2 coax rf jumpers coming off the top of the eNB)
Nokia Mini Macro 2.5 on Samsung NV Macro
Nokia Mini Macro 2.5 on Alcatel-Lucent NV Macro
I'm sure there will be some that have to be replaced. Especially any that are probably around two years old or older. But they mentioned that they exelected to have some sort of replacement program or at least heavy discount for those that are forced into a new phone.
As with any corporate promise, I think people should still be prepared to buy new phones in the event T-Mobile doesn't update phones to support VoLTE.
Sure, those older phones will work with WCDMA fallback, but voice coverage won't be the same. 1900 GSM isn't as robust as 1x1900.