Edit in JSFiddle

//extend the A object with Backbone.Events methods
var A = _.extend({name:'A'}, Backbone.Events);
var B = {name:'B'};

//when the event on A is called, set the callbacks context (i.e. this) to B
A.on('sayMyName', function () {
    console.log(this.name);
}, B);

//trigger sayMyName
A.trigger('sayMyName'); //logs B because we adjusted context of callback