Thank you krambriw, your answer pointed me to the right direction for what I wanted!
The trick was executing the
initMap(data)
google maps callback function in place of your " update(data) ".
Then I could normally access the msg returned from the query like
for (var a = 0; a < data.length; a++) {
var tmpLat = data[a].lat;
var tmpLng = data[a].lng;
var marker = _newGoogleMapsMarker({
_map: map,
_lat: tmpLat,
_lng: tmpLng
});
}