The cid is a client id and is never send to the server.
When Backbone model save is called successfully the data received from the server are set on the same object, not creating another model.
So your are manually adding the two models to your collection, try to remove this line :
channel.bind('new_ticket', function(data) {
var ticketDataObj = jQuery.parseJSON( data.content );
// create a new method addAndMergeTicket
app.ticketsView.addAndMergeTicket(ticketDataObj);
});
In this new method, before you add the model to the collection, iterate through the collection models and if you find that it already exists don't add it again