The EK ban is official. Its a 3 year block on you joining Emirates, although I would not be surprised if this get extended to 4 or even 5 years if they keep losing guys to Emirates. As for the other lot down the road its a bit more complicated, there is no official ban that I am aware of but I do believe that if you join them you have to move to Abu Dhabi and If you have any length of time left on your Dubai visa they would think twice about taking you on.
Something has definitely slowed down the rate of guys going to Abu Dhabi so it is either as I mentioned above or the two companies have come up with an agreement to stop guys going down there. It's all rumour and guess work at the moment but something is stemming the flow.
Instead of dirty tricks and behind closed door agreements all they need to do is sort out the T & C's and rosters and then people might actually want to stay here. Simple !!