Pegar resultado de ajax em variavel global e usala em dois momentos

FactoryOrgaoLotacao

OrgaoLotacaoModule.factory('OrgaoLotacaoFactory', ['$resource',
    function ($resource) {
        return $resource('/api/con-orgao-lotacao/:id', {}, {
            get: {method: 'GET'},
            save: {method: 'POST', requestType: 'json'},
            query: {method: 'GET'},
            querySiglas: {
                method: 'GET',
                url: '/api/con-orgao-lotacao/?_method=get-siglas'
            },
            remove: {method: 'DELETE'},
            delete: {method: 'DELETE'}
        });
    }]);

FiscalModule

 FiscalModule.controller('FiscalListaController', ['$rootScope', '$route', '$filter', '$scope', '$http', '$timeout', 'uiGridConstants',  'FiscalFactory', 'ContratoFactory', 'OrgaoLotacaoFactory','localStorageService',
    function ($rootScope, $route, $filter, $scope, $http, $timeout,uiGridConstants, FiscalFactory, ContratoFactory,  OrgaoLotacaoFactory,localStorageService) {

 var siglas; //Auqi a variavel global
    
      //Aqui eu estou p=recebendo os dados via ajax na minha factory
    
      OrgaoLotacaoFactory.querySiglas(function (response) {
          siglas = response.result;
       });
});
      

UI_GRID Angular na FiscalModule

  $scope.gridOptions.onRegisterApi = function(gridApi){
            $scope.gridApi = gridApi;
            gridApi.rowEdit.on.saveRow($scope, $scope.saveRow);
        };


        

        $scope.gridOptions.columnDefs = [

        {name: 'id', enableCellEdit: false, enableFiltering: false,displayName: '#', width: 60 ,
                cellTemplate: '<div class="ui-grid-cell-contents text-align-right"><a ng-href="#/fiscal/{{COL_FIELD}}">{{COL_FIELD}}</a></div>'},
            {name: 'sNome', displayName: 'Fiscal', width: '30%', filter: {condition: _.searchMultiTerms}},
            {name: 'sMatricula', displayName: 'Matricula', width: '25%', filter: {condition: _.searchMultiTerms}},
            {name: 'bSigla', displayName: 'Orgão Lotação', width: '20%',
                filterHeaderTemplate: '<div class="ui-grid-filter-container" ng-repeat="colFilter in col.filters"><div select-dropdown-array></div></div>',
                filter: {
                    options: siglas,//Aqui eu quero usar a variavel global com resultados
                    condition: function(searchTerm, cellValue) {
                        if(!_.isEmptyVar(cellValue))
                            return cellValue.toLowerCase() == searchTerm.toLowerCase();
                    },
                },
            },
            {name: 'sNumeroContrato', displayName: 'Numero do Contrato', width: '20%', filter: {condition: _.searchMultiTerms}},


        ];