The mount and title are given to any player within 10hrs of the gong being banged for the first time.
http://wowwiki.wikia.com/wiki/Gates_of_Ahn%27Qiraj "Note: The Bang a Gong! quest (and therefore, the legendary mount) is only available during the main war event which occurs upon the initial ringing of the gong and lasts 10 hours thereafter."
You also have to remember, most of the quest items for this quest is ONE person loot. This means each raid reset for each raid, only one of the 40 people may get the quest items. I am sure plenty of guilds will have a scarab lord and the mount, but for one or two people. That is, if it is scripted right.