Actionscript 3 :: Send Events Between Objects On Same Level (Global Event Manager)?

I came to the point where I need to communicate between 2 objects (let's say Tank and the Cannon). It is tile game, and when the Tank approach specific tile I need my Cannon to shot the Tank. When Tank gets that specific tile I want to dispatch some custom event and have listener in Cannon class body to make the shot happen. Other way I would have to check in ENTER_FRAME loop (inside Cannon body class) if the Tank touched tile that runs the Cannon shooting - but this is not elegant and efficient. The issue is complicated by the fact that the Cannon and Tank are added to the Engine (document class) and can't simply hear for each other, because they seat on the same level in display list.

Initially I could addEventListener to the Engine, but this way my document class would enlarge to the XXL size (all listeners functionality, all methods for game etc). What I would accomplish is to have event listener in every Cannon object (defined in body class) listening for Tank's dispatching the event. I saw some 'Centralized Event Manager' article in the net, but can't download full classes [url]...