For ajax stuff, this is under rewrite. So now my head is full with the new code.
What is the "getRendering" function ?
did you tried :
jQuery("#_ajax_items_select2").ajaxComplete(...)
Because you are asking the event over the document object, but I never put my code on the document. It might be attached to the field.
The new Ajax framework is called 'Hook' and some parts are already available in JDom, but still under coding.
In future there will no be any code in the view. only XML, such as a normal field.
And the Hook framework permits overrides of plugins. Same as JDom.