Besides brass, no one. Walthers currently owns exclusive licensing rights in the USA with Amtrak to the Phase V paint scheme for locomotives. Thats why Atlas's Phase V AEM-7s lack the logo, and the Bachmann offerings all say Acela. (which isn't entirely the only reason why. A while back, Amtrak attemped to rebrand everything in the Northeast as Acela. When David Gunn took over Amtrak, he quickly scrapped that idea, so now except for the Acela express, nothing is branded Acela anymore. However, there are some Amfleets still in the Phase V scheme still running around, and Bachmann makes them in HO scale)
Since Athearn is the only manufacturer making P42s in HO scale, Athearn makes the Phase V engines for Walthers (hence the Athearn Collectables box)