gold plated standards would not have been needed for this line. never had them, never needed them.
SAR operated it with single 830s, OBs & OBFs. AN did too but got it up to 22 x AHGX and double 830s, perhaps showing what was possible with the right focus and motivation. (too bad they didn't display such savoir faire elsewhere.)
it was only post standardisation that it attracted heavier engines, GMs, 600s and 422s. not sure it ever saw a 930.
the line doesn't have - & has never had - any traffic that would require more than a light standard of track & ROW. it was operated on a seasonal-only basis since 1973 if memory serves correctly. evidently the small tonnages of general loading & stock were not sufficient for even the SAR to worry about & those were the only things that might have been time sensitive. so, provided bulk super & grain wagons oould get along the line at 10mph i'm sure it was reasonably viable.
i think it is a bit of nonsense which has unfortunately been accepted by the rail industry that heavy axle loads and great hulking ballast shoulders are needed on a branchline. accept such loony parameters in a country of only 20m & there'd only be about twenty viable lines in the country. -most likely what the road industry would like.
i agree with bing that if this were the US, the line would be a candidate for operation -by someone. it is on the right gauge, has a bulk traffic ideally suited to the low train speeds pertaining, a grain terminal equipped for current wagons & can take a variety of lighter locos.
what is needed, i would guess, are slightly less witless privatisation arrangements which decree that operators either krapp or get off the pott.
ie, you don't get to sit on lines you have no intention of running revenue earning trains on. they go up for bidding to other operators.
under such an arrangement, it would be less than remarkable for an existing operator to suddenly find reasons to run trains there, if only to keep potential competitors off his patch.