Information on the secondary admissions arrangements for Sept 2008 have been published on the Birmingham LEA web site:-
These don't appear to have changed materially from the 2007 arrangements apart from the fact that you can state your preferences online at any time up to the 9th Nov 2007, which is after all of the Birmingham Grammar and KE Foundation Grammar 11+ exams have taken place. You do obviously still have to complete a separate form to enter the exam.
The allocation date is still the 3rd March.
Don't know what the situation is for those that live outside Birmingham - the dates will vary.
So it looks as though Birmingham had decided not to adopt the recommendations stated in the revised School Admissions 'Code of Practice' - ie let parents choose the preferences after they know the results of the 11+ exam tests.