Yes, our LoRaWAN stack is ready implemented and runs securely on the isolated M0+ core inside PSoC6.
You will have full and unrestricted access to the M4 core for your own application. Communication with the LoRaWAN stack is possible using a LoRaWAN API. This LoRaWAN API is using IPC calls between the M4 and the M0+ to transfer the commands and data.
The datasheet all provides all the information on how to use the LoRaWAN API.