Only a guess Sulla 1 but could they be for SCT. They've been struggling with motive power problems for quite a while as as you are probably aware have CFCLA VL class units on hire. I have tried to enquire around the place what the performance of their Chinese units has been like but very hard to get specific details.
This would involve conversion of the GT42CU-AC to standard gauge.
While not that hard, it would require new bogies being built.
There are two JT42Cs based on the WAGR NG S design at Weipa, and a similar bogie design could be used.
Being only 3030HP and having small traction motors would reduce their usefulness to SCT compared to their other locomotives.
However, they are available for sale.