Apple uses a Qualcomm baseband chip. They share the capabilities with other manufacturers, but Apple is working on their own baseband chip which they expect to ship in 2023.
But they don't have to implement CDMA2000 like other countries' models even though it uses Qualcomm chip.
The chipset the qcom modem they are using probably supports it. Would depend on the firmware and sometimes a grounded pin if it is on or not. Much like FM radio in many of these devices is 'there' but not turned on/wired up. For the new chipset that Apple is making I seriously doubt they would support that standard, esp if the big telcos are turning it off. But it would depend on what sort of contract they have with the telco.