A Sony executive is on record saying the Sony designed the Zeiss lenses. Sony also is in total control of the manufacture, marketing and sale of the lenses -- contrary to Zeiss' previous arrangements with camera makers.
I would no go so far as to agree with the suggestion that Sony is just using the Zeiss name. But I do believe, from all evidence to date, that Zeiss' role with the ZA lenses is more as a collaborator, or as a consultant, who has some sign-off authority on the final design. But make no mistake, Sony is in total control of this show from start to finish. Sony's name is even large on these lenses than Zeiss' -- and when have you EVER seen anyone else's name on a Zeiss lens but Zeiss'?
The following is what the Zeiss website says about the ZA lenses:
ZEISS lenses for Sony digital cameras are developed by lens designers at the Carl Zeiss plant in Oberkochen, Germany. This includes all required quality assurance measures (test methods, test criteria, test devices, test procedures, lens performance target values, etc.) The lenses are then made in a lens production facility jointly chosen by Sony and Carl Zeiss. Quality assurance specialists from the Carl Zeiss plant in Oberkochen implement the ZEISS quality assurance system in the chosen facility. Many ZEISS optic measuring systems are installed. Carl Zeiss audits the lens production areas on a regular basis.
Note that a Zeiss "Sonnar" or "Planar" or "Vario-Sonnar" or "Tessar" etc. are VERY specific designs with some VERY specific criteria that are completely different between the different designs. It is not just merely slapping a 'label' on them.
Also note that even in the Sony/Zeiss dSLR lens range, there are 2 categories: The professional-grade Full-Frame lenses and an APS-C-only DT lens. These are 2 completely different animals.
The Zeiss 135mm f/1.8 Sonnar ZA, is a HUGE and heavy beast with full metal body and even the hood is completely metal. The quality from this "Sonnar" design is also mind-blowing and in the "Excellent" range, corner-to-corner, right from wide-open. You simply cannot get better than that.
The Zeiss 85mm f/1.4 Planar ZA is also full metal body, including the hood. Extremely high quality professional-grade lens with the same "Excellent" quality from wide-open.
The Zeiss 24-70 f/2.8 SSM Vario-Sonnar is another from their high-end Pro-grade range of lenses. Ultra-high quality that beats down the new Nikon 24-70 f/2.8 in sheer resolution, when tested on APS-C. Since this is a 2008 design, specifically optimized for FF sensors, I would opine that the quality on FF would also be exemplary.
The newly announced Zeiss 16-35 f/2.8 SSM Vario-Sonnar would also be expected to be of the same ultra-high-end quality as the above mentioned 24-70 f/2.8 Vario-Sonnar.
Now comes the APS-C-only "Zeiss" lens, the 16-80 f/3.5-4.5, which is a whole different level from any of the above mentioned Pro-grade Zeiss lenses. This particular one is pretty iffy from a build quality-perspective, with a plastic casing and is clearly intended as a high-end kit lens for APS-C products. The optical performance is however, pretty good, albeit at a different level from the all-out-pro-grade Zeiss lenses in the range.
Note that every single one of the professional-grade Sony/Zeiss lenses, have a unique ZEISS serial#, *in addition to* the unique Sony serial number on the lens.
I think the fact that the lenses are designed in Germany with all the design criteria surrounding it, and testing methods, and made using the Zeiss-exclusive Schott glass (only pro-grade ones) is a good thing.
The fact that these German designed lenses are actually assembled in Japan, is even better, since there are none better than the Japanese, when it comes to precision assembly methods and are arguably even better than an equivalent assembly work done in Germany (my opinion).
German design, Japanese assembly - best of both worlds !