Thank you both very much for the helpful answers.
I am actually enquiring on behalf of a friend, I was able to set up mine as Exchange two weeks back but it appears that many are not being able to.
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If you've set it previously (prior to January 31st) and you're still using the same device then you won't have a problem setting up Gmail via the Microsoft Exchange setup. However, those who have never set it up that will not be able to and current users will not be allowed to set it up that way with devices other than those it is currently setup on even if they restore from a backup.