directives.js

angular.module('SvgMapApp').directive('svgMap', ['$compile', function ($compile) {
    return {
        restrict: 'A',
        templateUrl: 'img/Blank_US_Map.svg',
        link: function (scope, element, attrs) {
            var regions = element[0].querySelectorAll('.state');
            angular.forEach(regions, function (path, key) {
                var regionElement = angular.element(path);
                regionElement.attr("region", "");
                regionElement.attr("dummy-data", "dummyData");
                regionElement.attr("hover-region", "hoverRegion"); //<--- Add this
                $compile(regionElement)(scope);
            })
        }
    }
}]);

angular.module('SvgMapApp').directive('region', ['$compile', function ($compile) {
    return {
        restrict: 'A',
        scope: {
            dummyData: "=",
            hoverRegion: "=" //<--- Add this
        },
        link: function (scope, element, attrs) {
            scope.elementId = element.attr("id");
            scope.regionClick = function () {
                alert(scope.dummyData[scope.elementId].value);
            };
            scope.regionMouseOver = function () {               //<
                scope.hoverRegion = scope.elementId;            //<--- Add this
                element[0].parentNode.appendChild(element[0]);  //<
            };                                                  //<
            element.attr("ng-click", "regionClick()");
            element.attr("ng-attr-fill", "{{dummyData[elementId].value | map_colour}}");
            element.attr("ng-mouseover", "regionMouseOver()"); //<--- Add this
            element.attr("ng-class", "{active:hoverRegion==elementId}"); //<--- Add this
            element.removeAttr("region");
            $compile(element)(scope);
        }
    }
}]);

index.html

<!--...    -->
<div class="regionlist">
    <div ng-repeat="(key,region) in dummyData" ng-class="{active:hoverRegion==key}"> <!-- Change this -->
        <div>{{key}}</div>
        <div>{{region.value | number}}</div>
    </div>
</div>
<!--...-->

main.css

/*...*/

.regionlist > div.active {
    font-weight: bold;
    background-color: lightblue;
}