Check out the information in NAT Doc 007 (available for download on the internet). At this current time RCP240 and RSP180 is required for PBCS Tracks only. But the rules are continually changing and there is another major revision happening in late Jan 2020. PBCS tracks are assigned on a tactical basis each day and can be found in the Notes section of the NAT Track Message.
Outside of PBCS on a NAT Track (FL350-390) requires CPDLC and ADS-C.