The industry is WAY more complicated then that Vyrus and the number of companies too vast. Specialty contractors won major packages from Uni (huge packages that included many things they don't even do) and their subcontractors either bid too low or just made piss-poor business decisions. FACT: In the end, many of the things you see in the WW were passed on and on from later defunk subcontractor to subcontractor AND, in the end, even though the final sub finished the project... they too went out of business.
Indeed, some of the stuff that was completed by the subcontractors were rejected by Uni and then had to be reworked by the contractor that never specialized in that area of art in the first place. It was nasty, and many of the artists that created what is currently on view visited not recognizing that which they thought was finished. Sorry to go on so, but I find all of this fascinating.