Tronman. I believe your assumption is correct, although it looks to me like the axles actually pivot around the u-joints at the pumpkin and serve as control arms. The wheels will be straight vertical only in one position of the suspension, with positive camber (top of wheel out) with the suspension unloaded and negative camber if overloaded.
This is similar to the early Corvette rear suspension (I'm only familiar with the '63), although that car has trailing arms that included wheel bearing carrier, lower control arms and the non-telescoping axle shafts acting as upper control arms with u-joints both at the differential and at the wheel bearing carrier. The Corvette IRS kept the rear wheels mostly vertical.
