feather44, I think you will find that the DXB controllers (and many others - but not all) will only use time for departure as that is all they are allowed to use.
So you have either 2min, 3min or 4min depending on the combination of aircraft weight category and if the second departing aircraft is an intersection departure (greater than 150m from the first departure point = add 1min)
Also you will probably find that any decent controller will be uttering those magic "cleared for take off" words when you have about 45secs remaining for the time to run as it is measured wheels up to wheels up. They want you to be rotating at 2mins+1 sec or 3mins + 1 sec. Nothing more infuriating than a pilot who thinks he knows about wake turbulence and will not roll until the 2mins has elapsed.
If you are not happy with the ICAO standards then take it up with them
