Do you have any sources or confirmation about that?! The only floormap where you can see a barrier on the pitch, is the map of Croke Park Dublin. All other maps only seems to have 1 big GA-area (+ Red Zone).
Although it makes sense for me if the GA-floor in ALL STADIUMS will be seperated into two parts by a barrier, just for safety reasons. That would be an extra advantage for fans who are queuing early because with a barrier (and wristle bands to enter this area) it will be easier to leave your place to get some drinks or going to the toilets.
If there is only one big area on the floor, it's really a hell to leave your spot to get some drinks etc, so it means you have to stay on your spot the whole evening (and that's a long time because doors will be open already at 16h30, and I don't see U2 taking stage before 21h)
I haven't got sources or confirmation, but it has been done like this for decades now. Since the ZOOROPA Tour this system was used in the Netherlands when playing in stadiums, so you can be sure it will be like that on this tour too.
They'll let about one third of the total amount of GA tickets in this section, which is quite a lot, so just start queuing at noon and you're quite certain of a spot inside this section. If you want to be at the very front then you'll have to show up earlier. But if you don't mind to be 20 meters from the stage and have plenty of space around you and no people pushing you in the back, you are fine.
In Amsterdam they create two queues and let people in at the same time when the gates will open.
I don't remember this from 360 though..... I went to Dublin and Brussels, there was no 'front pitch' Did Amsterdam have one?