Try to catch you map in a log

function loadCableGeom(){
console.log(yourmap);
_this.map.data.loadGeoJson('https://storage.googleapis.com/mapsdevsite/json/google.json');
    _this.map.data.setStyle({
      fillColor: 'green',
      strokeWeight: 1
    });
    console.log("LOAD");}

If it doesn't work try to pass it into your function with a parameter function loadCableGeom(map) Maybe your _this.map doesn't work.

Try to catch you map in a log.

function loadCableGeom(){
  console.log(yourmap);
  _this.map.data.loadGeoJson('https://storage.googleapis.com/mapsdevsite/json/google.json');
  _this.map.data.setStyle({
    fillColor: 'green',
    strokeWeight: 1
  });
  console.log("LOAD");
}

If it doesn't work try to pass it into your function with a parameter function loadCableGeom(map). Maybe your _this.map doesn't work.