Not to sure what you can do under the JAR system, but you "CAN'T" log any supernumerary flying under the Kiwi and Aussie regs. The Airline I fly for generally only has a safety pilot in the jump seat when a pilot in either operating seat has very little to on the line, ie initial line training, the other pilot will always be an experienced training captain. The trainees have always completed the sim and done a post sim excercise in the real aeroplane with a checkie prior to going onto line, hence the trainee logs the hours, and not the safety pilot.