From their document, https://developers.google.com/maps/documentation/javascript/events, 
User events (such as "click" mouse events) are propagated from the DOM
  to the Google Maps API. These events are separate and distinct from
  standard DOM events.
As far as I understand, only google maps event can be applied to google maps objects including markers, shapes, etc.
That was the bad news.
Good news is you still can use on-click event to manipulate $scope variables and events. There is not much difference as long as you use a function for this event. 
I will keep investigating if there is work-around, so that we can use AngularJS Event into(i.e. ngMouseenger, ngMouseleave. ngMouseup, ngClick, etc
A working example using on-click is at plunkr to satisfy your requirement.
http://plnkr.co/edit/6qvS0vUYkqVHZ3t6qmn2?p=preview
This is script part
  $scope.myVar = 1;
  $scope.changeMyVar = function(event) {
    $scope.myVar+=1;
    $scope.$apply();
  }
This is html part
  <map zoom="11" center="[40.74, -74.18]">
    <marker ng-repeat="p in positions" 
      position="{{p}}" title="{{p.toString()}}"
      on-click="changeMyVar()">
    </marker>
  </map>
  myVar : {{myVar}}  Click a marker to increase myVar
To know more about angularjs-google-maps events, please take a look at the example about event