I certainly don't know for sure, but I don't believe, that AIBs are doing any board manufacturing for the 58xx series at this time.
Economy of scale doesn't make it sensible. It's cheaper for one factory to purchase a million RAM chips and have it all shipped to said factory, than for 10 factories to order 100,000 each and have them shipped to 10 different facilities around China. Same goes for PCBs, capacitors, all the components.
My MSI 5850 has the AMD corp. logo silkscreened onto its PCB. So does every 58xx card I've seen pictured across the web. I strongly believe that reference design parts are all coming from one place fully dressed with components, and AIBs are receiving these finished cards, then dressing and installing the coolers at their own facilities. Every AIB has their own junk that they plaster onto the coolers, and some are offering their own cooling solutions. But every PCB I've seen has the AMD logo, and at the very least, the same brand and style of chokes on them.