Its unlikely. They had pre-existing infrastructure for this via their Apple Messages For Business[0] program, which includes all the backbone to show that the account is verified (including the checkmark and info tab). This appears to be an extension of that for consumer accounts
I wouldn't say they "gained access to iMessage network".
They figured out a weakness in Apple's authentication that allowed a user with a fake serial # to authenticate. Apple is slowly making it more strict/checking the serial #s better (my opinion/guess).