By the photo title they are Elizabeth Body Assembly Plant vans heading to Dandenong Vehicle Assembly Plant. They are painted and hard trimmed. This is the same as how they came out of Elizabeth's BAP to be assembled in Elizabeth's VAP but they got sidetracked to Dandenong VAP instead. They will have Elizabeth BODY tags fitted. They will appear in the records in two places: at Dandenong, and also as a gap in BODY numbers in the Elizabeth records equivalent to the "pack" amount that fits on the train. After 11/77 they appear more obviously as a gap in the Elizabeth PSN's.

See that factory fitted side windows? Can't get better evidence than that!

Great photo.