NG/BG splitter have been around for a very long time in SA. They were at Gladstone as I recall in the steam era even on the main lines where they ran over the sh pits in the station yard and at the turntable which had concentric BG and NG tracks.
I would dare suggest such splitters were around from when the BG and NG systems first met back in the 1880s.
As for milling rail heads SAR certainly had the technology. There were two very large planning machines at Islington which only got cut up? about 3 years ago. these machines were big enough to plane the frames for 720 and 520 class locos
Agreed re BG/NG splitters, I was reffering to SG/BG ones. AFAIK there were no SG/BG spitters (like on the Mile End TT) at Peterborough, Gladstone or Pt Pirie that swapped the common rail from one side to the other. Certainly none on the 40'=1" plans I have of those yards, nor from all the photos I've seen.
None at Albury/Woodonga, Oaklands or Tocumwal either.
I believe thery first appeared at Keswick, possibly earlier in the Dry Creek/Cavan area and Mile End, though I'm unsure about that as there was no real necessity for it.
SG and BG was rarely mixed and when it was there was only a frog and either a point blade or a (dunno what they are called - basically a long casting that used either the flanged diverging rail/parallel rail on the opposite side to steer the wheelset) I have all the AN BG/SG turnout plans too, and there are a heap of them - Every Combination of common rail was catered for so the necessity of splitters was basically restricted to swapping the common rail on platform 2 at Keswick to allow for the BG loading gauge (later removed and the common rail is now the same as Platform 1 and 3) and TT's AFAIK.
Any info that can correct that is most welcome.