In that case, the attack would not need much cooperation on the part of the OEM/ODM. The Intel chipsets could be flashed enroute to their manufacturing plant. They might not want the malware to go many places other than the intended target, which is why they would likely want some cooperation to ensure that they only make it to the intended target, which is why I say not much cooperation rather than no cooperation. Anyone from Apple inspecting the factory might not realize it.
I probably should elaborate that this attack assumes that the chipsets have internal flash. So far, I have only heard of this from a coreboot developer and upon doing Google searches, I cannot find any sources for that information. :/
