data.js

// Data passed to Placester search during AJAX request
[
  {"name":"iDisplayLength","value":9},
  {"name":"iDisplayStart","value":0},
  {"name":"sEcho","value":2},
  {"name":"context","value":"custom_listings_search"},
  {"name":"import_id","value":"54d18daab1c93c67b4000001"}, // <== The value is getting passed to Wordpress's ajax handler
  {"name":"location[address]","value":""},
  {"name":"location[neighborhood]","value":""},
  {"name":"metadata[min_price]","value":""},
  {"name":"metadata[max_price]","value":""},
  {"name":"metadata[min_beds]","value":""},
  {"name":"metadata[min_baths]","value":""},
  {"name":"sort_by","value":"total_images"},
  {"name":"sort_type","value":"desc"},
  {"name":"action","value":"pls_listings_ajax"},
  {"name":"saved_search_lookup","value":"/-628839853"}
]

form.html

<input type="radio" id="results-mls-switcher-greenville" value="50464c56d23a547a29000013" name="import_id" checked="checked">
<label for="results-mls-switcher-greenville">Greenville</label>

<input type="radio" id="results-mls-switcher-spartanburg" value="54d18daab1c93c67b4000001" name="import_id" >
<label for="results-mls-switcher-spartanburg">Spartanburg</label>