An opinion, very broadly until recent years the various State Government Systems did not run that many Goods trains that were always multiple headed and often on route shunting was required!
More recently this century nearly all at Goods trains are hauled by multiple units. However the culture of using booster/slug non drivable units has remained.
These units like V544 are relatively young and have not seen a lot of real use.
The three XRB units are stored that can mean several things. One as the word implies or stored and usable components removed making the return to traffic totally uneconomic.
So could they have a new lease of life as all of the recent Portland Grain trains for instance are triple headers as are most of Pacific Nationals Steel and Melbourne Perth trains.
Over to People who know facts and current Locomotive ideas and policy of use.