@ih, my comment was to try to illustrate the fact that NR had to be forced (by legislation) to improve conditions for disabled people. Otherwise those modifications would have been carried out much sooner. I get the feeling that cyclists, who might all be passengers, are basically just pests who need no special treatment that provides equality of access, but public pressure made NR relent.
As gkgk noted, I think the presence of the pedestrian crossing, and the habit of cyclists to race down hills and run amok in public spaces, was the single reason why the south ramp was not an option. Whether or not this would have held out in real life — I suspect not — is not up for argument anymore it seems. Public perception of cyclists has thoroughly polluted every kind of public space design thinking, despite no-one remembering all of the good drivers and good cyclists that we enounter every day. It's human nature to remember negativity.
In some respects, the 1960s idea of reducing Waverley to a local station and building (or rebuilding) Princes St Station at ground level might well have been the better option overall. Waverley is, to all intents and purposes, a glorified underground station with complex access arrangements.