Officially, CPDLC is still undergoing trials on the North Atlantic.
From the NAT-PCO Website:
"Phases 1 & 2 CPDLC Operational trials were commenced by NavCanada (Gander) and UK NATS (Shanwick) in Autumn 2002 and Phase 3 commenced in December 2003. Iceland (Reykjavik) and commenced Phase 1& 2 operational trials in 2005. Portugal (Santa Maria) commenced Phase 3 operational trials in the last quarter of 2006. A fully operational CPDLC service is in operation in the New York FIR."
"Gander, Reykjavik, Santa Maria and Shanwick plan to provide a full CPDLC service in the fourth quarter of 2007"