Handle multiple geoJSON layers in a Leaflet.js angular directive. Original code by @pospi, slightly modified to support the pointToLayer option.

leaflet-multi-geojson-layers.js

/**
 * Service to manage geoJSON layering with Leaflet.js' angular directive, which only allows 1 set of geoJSON data.
 *
 * Assuming you have a leaflet directive with its 'geojson' attribute set to `geojson`, usage is as follows:
 *     var layers = new GeoJSONLayers();
 *
 *     layers.addLayer('myLayer', geoJSON, function(feature) { return { fillColor: '#00F' }; });
 *     $scope.geojson = layers.get();
 *
 *     layers.removeLayer('myLayer');
 *     $scope.geojson = layers.get();
 */
angular.module('MyApp').factory('GeoJSONLayers', [
    function() {
        var handler = function()
        {
            this.clear();
        };

        handler.prototype.clear = function()
        {
            this.json = {
                type : "FeatureCollection",
                features : []
            };
            this.layerStyles = {};
        };

        handler.prototype.addLayer = function(layerID, geoJSON, styleCallback, pointToLayerCallback)
        {
            this.layerStyles[layerID] = styleCallback;
            this.pointToLayer = pointToLayerCallback;

            // tag features with their assigned layer
            geoJSON.features.forEach(function(feature, i) {
                feature.properties.__LAYERID__ = layerID;
            });

            // merge into current objects
            Array.prototype.push.apply(this.json.features, geoJSON.features);
        };

        handler.prototype.removeLayer = function(layerID)
        {
            var feats = this.json.features,
                i = 0;

            delete this.layerStyles[layerID];

            // remove relevant geoJSON objects as well
            for (; i < feats.length; ++i) {
                feature = feats[i];
                if (feature.properties.__LAYERID__ == layerID) {
                    feats.splice(i, 1);
                    --i;
                }
            }
        };

        handler.prototype.__handleStyle = function(feature)
        {
            if (feature.properties['__LAYERID__'] === undefined) {
                return {};
            }
            return this.layerStyles[feature.properties.__LAYERID__](feature);
        };
        handler.prototype.__handlePointToLayer = function(feature, pointToLayer)
        {
            return this.pointToLayer(feature).options;
        }
        // return geoJSON data for assignment to scope
        handler.prototype.get = function()
        {
            var self = this;

            return {
                data: this.json,
                style: function(feature) {
                    return self.__handleStyle.call(self, feature);
                },
                pointToLayer: function(feature, latlng) {
                    return L.marker(latlng, self.__handlePointToLayer.call(self, feature, latlng));
                },                
                resetStyleOnMouseout: true
            };
        };

        return handler;
    }
]);