In the comments to the previous post, Nicolas Derome linked to an interesting residential development outside Toronto (very close to a major planned DPZ project) which appears to have adopted the garage-parking-under-square approach. Google's streetview has covers this development, allowing you to explore it on your own, but in the aerial view below the essential elements are all visible:
The design is very much Garden City, resembling a somewhat denser Radburn (or any one of dozens of low-rise American public housing projects) with segregated paths for automobile and pedestrian traffic. In the absence of any use but residential, there is no pretense of urbanism here. Without places to walk to, the advantage gained by stowing the cars underground is not exploited.
Could a similar design be adapted to traditional urbanism? I've shown the example of Bastia, or a larger city such as Mannheim, or Savannah, but in each case the underlying theme is simply moving the built elements closer together, whether in a grid or in a more organic layout:
Would any attempt to integrate garage ramps into a dense urban environment fall victim to "overblown traffic engineering and design codes," as Marc mentions in the earlier comments? It is difficult to imagine anything as modest and and sensitive as the Bastia and Mannheim examples being allowed in the United States, but this Canadian development shows at least that it can be an economically viable design approach.