this is not accurate/correct (anymore). there was a point in time when Melbourne was not "the worlds most livable city" and as such we have/had a train network from the 1950s, including the control systems which mostly ran up untill 2009 under connex' tenure post privatisation.
Metro Trains which is a consortium took over the train network at this point and was contractually obligated by the state to upgrade all core and edge technology systems.
I worked at MTM circa 2016/2017 and all the truly legacy operation control systems had been replaced.
there was a heap of funding allocated for fun things like maintaining OCMS/IT systems and updating customer facing/passenger information systems.
Not sure how I missed this, but the comment on the mastodon post points this out too:
> that emulated PDP-11 system was replaced in 2014-15 by an off-the-shelf “Westrol” system from vendor Invensys.