Zend_Json is not an AJAX framework, it's only purpose is to serialize PHP code into JSON: http://framework.zend.com/manual/en/zend.json.html
I do not know MyBic but there shouldn't be any problem to migrate your application under ZF -- you have to create your controllers and actions and instead of directly call them from your URL bar, call them through XHR-s. Ádám
