They clearly don't have the old code base, workforce to hypothetically adapt it to VoLTE, or factories to manufacture the phones. New Nokia TA-xxxx phones use MediaTek/Unisoc(Spreadtrum) SoC and MediaTek MAUI software rebranded as "S30+". Which means those are reskinned Chinese phones.

Old Nokia had RM-xxx or RX-xxx model numbers, so it's also clear that some of their corpo structure did survive.