Thanks for the correction regarding ECC protection in modern GPUs. Since documentation does not have a unit test, it can easily be incomplete or inconsistent, at times even plain incorrect. I note that the quoted text about the Quadro does not preclude ECC protection on registers and caches, it is simply silent on the issue, possibly because this is not an important detail for typical Quadro customers.
If you must ensure that full ECC protection is available in identical fashion on both Tesla and Quadro, I would suggest getting in touch directly with NVIDIA through dedicated Tesla support channels.
I certainly appreciate why such assurances would be important in the context of GPUs used in medical devices: in the context of medical imaging I have stated before that ECC is desired because one would never want to have to worry whether a discolored spot in an image is an artifact caused by a flipped bit in GPU memory, or a cancerous lesion.