Whilst the the 2 NSW Parcel Vans in the photos are example of what they looked like, they are certainly not being used as parcel vans but as some sort of test cars as parcel vans had long gone by then.
The yellow one ex parcel van C3558, ex 3992 Special Profile Car SPC-1 was a "Profile" car, I think at Elcar it was used to profile station track alignment after work in the suburban area, whilst the green one was ex C3555, to ex C3595 Westinghouse Brake Test Car, to C3993 the for testing new brake blocks. This car had holes with hinged hatches in the floor to observe the brake blocks under test. The green was Hawthorn green. I disagree with the comments above from nswtrains with the fact that parcel vans did last around to the same time as single deck suburbans were withdrawn. I know that some cars were used as "equipment" cars for running around the system picking up seats & window frames thrown out of suburban trains at the time roughly mid 1990's.