These prints are indeed cibachrome backlights.
Jeff Wall bought the same Ilford Processor that I have in my shop , except his is quite larger.
This machine is dedicated to his work and maybe a few select friends that he allows to print on the machine.
I have heard that Jeff may be indeed one of the worlds largest user of this Ciba back light product. The numbers that I have heard of his inventory purchases of this product this last year is staggering.
I am not sure how he is exposing the material but I would not be suprised if he did not buy a lightjet from cymbolic sciences for his photographic output.As well he would need a full blown mounting facility to accomodate the face mounting of these large pieces that he is famous for.
This investment in *photo gear* is not suprising to me as Ed Burtynsky basically has built a lab to fit his vision , with chromiras and large processors and finally the mounting shops to produce the very large work that both these artists produce.
The argument of whether the photographs are worth the price that these fellows are recieving, I will leave to the photo experts.
But I really do admire these two great living Canadian Artists who invest everything they own into their art.