That's the B end of a 44 class the same as the 930 South Australian Railways loco at least from 935 onwards the first 6 were were single ended 930's . The 421 class is like the Commonwealth Railways GM and Victorian Railways S class except it has a driving compartment in the B- end. Imho I reckon that the XD train is being hauled by a 421 Class as stated by Paul.
I think I may have to lie down that was a huge amount of foam even from me
Btw I googled the hell out of it