If you are unfamiliar with Whyalla (as I guess are most Australians) the former BHP line cuts across the highway South from Port Augusta just before entering the town itself (you can't miss it).
(You aren't driving from WA are you? If so you should check out Ceduna and Port Lincoln too.....)
A train is sometimes seen waiting at the top of the hill for entry to the unloader at the water's edge.
If 1907 isn't there, drive down the road next to the line on the town side until it stops (near the unloader). This takes you past what passes for Whyalla loco depot. There are spots where shots can be taken despite the massive fences.
Again, if you haven't found 1907, drive out towards Iron Knob until you reach the junction from the (abandoned) old line to the new mines to the South. You can often come across a loaded train on the way in, or if one is waiting in town, waiting just beyond the junction to the new mines.
By now you should have seen one or two trains. If 1907 wasn't on either, and wasn't in loco, you just have to wait.
Usually at least one train has two 1300s and one train has two 830s (unless they've changed things). 1907 usually works with a 1300 and could be leading or trailing.
The railway is South of the Iron Knob road and largely East-West, so photos can be taken during much of the day but not always with a lit front.
If nothing is happening you could drive out to Iron Knob and look at the preserved electric loco there, but Iron Knob is the sort of place that gives junkyards a bad name. (That's a bit unkind, I guess, but old mining towns do look pretty sad, generally).