It's a window-dressing or smoke-screening exercise to avoid hurting Dubai's public image and pride, while at the same time Abu Dhabi holds up its breath waiting for Dubai to (kneel) beg for former's much needed help. In doing so, Abu Dhabi will be quietly taking all Dubai's real value assets in a much formal shape and form and portray as being the saviours (Arab botherhood).
Still wonder if they really gain sth with this. Their investments drop in value a lot. I'd expect them to be the main investor in Dubai. It will take ages before they can cash with profit.