Shanwick and Gander control area (OCA) is an ATC environment with no surveillance radar capability. No surveillance radar capability means that the ATC cannot use radar to control aircraft. It is a non-radar environment. Therefore, the Oceanic controller receives estimates and position reports in order to provide procedural separation while flying in Oceanic FIR. In real life, Controller-pilot data link communications (CPDLC) and Aircraft Communications Addressing and Reporting System (ACARS) data-link communications is sent and received directly between controllers and pilots. And high frequency (HF) radio remains the primary means of voice communications.
On the VATSIM network, HF and ACARS is, per today, unfortunately not practicable. However, CPDLC and voice communication via Very High Frequency (VHF) is available. Not all controllers are equipped with CPDLC software, and as it is not a controller requirement, this is not a requirement for pilots to have in order to fly over the North Atlantic Ocean.
Download the Oceanic procedures document for further information.