Still not sure on the need for standardisation myself. Broad gauge track goes all the way into Appleton Dock, Swanston Dock and the Geelong Grain loop, all used regularly (Swanston Dock sees QUBE run trip trains of a weekend to Victoria Dock with the Deniliquin rake). It's not as if the Merbein freight (or the Tocumwal or Warrnambool for that matter) has to have its' loading transshipped part way down because there is no BG access, it goes all the way in.
The only possible advantage I could see standardisation allowing would be that another operator could run on the line eg. Aurizon or GWA, however QUBE currently runs BG services themselves (using their own wagons and locos, and others hired from CFCLA and GWA) so if someone wanted in, there's nothing stopping them getting BG equipment and doing so, and SSR's got stuff at Bendigo as well. If you were really desperate, SRHC's got a few locos not doing much these days after El Z went bust...