Actually after reading the microdata spec, there's a application/microdata+json format that would probably work better:

http://dev.w3.org/html5/md/#application-microdata-json

So you'd have an alternative resource

  <link rel="alternative" type="application/microdata+json" href="http://dev.w3.org/html5/md/#application-microdata-json" />

That file would look like this:

   {
    "items": [
    {
      "id": "http://example.com/events/2010/06/03/schweet",
      "type": "http://schema.org/Event",
      "properties": {
        "startDate": ["2010-06-03"],
        "location": [{
          "id": "http://example.com/places/my-crib",
          "type": "http://schmea.org/Place",
          "properties": {
            "url": ["http://example.com/places/my-crib"],
            "address": [{
              "type": "http://schema.org/PostalAddress",
              "properites": {
                "addressLocality": "Knoxville",
                "addressRegion": "TN"
              }
            }]
          }
        }]
      }
    }
    ]
   }

Who knows if Google will actually use that file though.