In the client controller script, literadius/views/js_css/xml_g_maps.js the function showMarkers(filter), check the token string for the checked token. This script could be modified to look for exclusive (multiple occurrences).
Another approach and a little more involved is to modify the SQL request on the server. This would also allow the checkbox action to request another set of data, which would query location requests based upon the AND conditional as well as the checkbox status.
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