Get Ideas from this: http://stackoverflow.com/questions/9781102/backbone-multiple-collections-fetch-from-a-single-big-json-file

bb-multi-collection

//Put your real collection constructors here. Just examples.
var collections = {
    Languages: Backbone.Collection.extend(),
    ProductTypes: Backbone.Collection.extend(),
    Menus: Backbone.Collection.extend()
};

function fetch() {
    $.getJSON("/url/to/your/big.json", {
        success: function (response) {
            for (var name in collections) {
                //Grab the list of raw json objects by name out of the response
                //pass it to your collection's constructor
                //and store a reference to your now-populated collection instance
                //in your collection lookup object
                collections[name] = new collections[name](response[name]);
            }
        }
    });
}

fetch();