The assist that the radar gave in the Stockholm / Andrea Dorea collision wasn't a matter of where the other ship would go. At the time there was no requirement for the radar system to have back lit (red, so as not to destroy watchstanders night vision) dials which would enable the operator to see at a glance what the settings were. According to the official report the operator thought the range from one ship to the other was actually greater than the other and commenced a turn across the others path. Once the turn began there was very little chance the other vessel could avoid the collision.
There are computer system radars called ARPA (Automated Radar Plotting Aids) which track other vessels and their positions as well as there predicted courses based on the objects apparent speed and course, relative to the course that the ARPA equipped vessel is on. It is a legal requirement for certain size vessels to be equipped.