On my bus it isn't possible to open the windows,
They don't swing out for emergency exit? Every coach I've seen has the windows hinged at the top and latched at the bottom.
This means that you can put a screen across the inside, open the window and prop it open through a small hole in the screen.
No, European coaches like mine are required by law to have emergency exit doors rather than using the windows to escape. In fact the windows don't even have frames as they are bonded directly to the steel. They are also very large, have curved glass and are double glazed (twin pane), so are incredibly heavy - but I love them, and they are one of the main reasons I bought my bus.