Slightly more information about how the lottery will run is posted here via the PCSB. It's from their board package for the PCSB meeting tonight (10/16/2013).
http://www.livebinders.com/media/get/NjI3MTk0MQ==
Probably the key section below. Looks like it will be run almost exactly how DCPS has been running their lottery. No info on number of spots available to select schools.
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How does the lottery process assign students? How many schools will families be
matched with and can they be waitlisted?
Before the lottery is run, schools will have an opportunity to verify sibling
status for applicants who indicated that they have a sibling who is currently
enrolled at that school. Applicants will then be given a sibling preference as
appropriate.
Each applicant will be given a unique random number. The algorithm will
assign students to their best preferred school using the random lottery
number to break ties when there are more students than seats available.
Each student will be matched with no more than one school and waitlisted at
any schools they ranked higher than their match. For example, if they are
matched to their 4th choice, they will be waitlisted at their 1st, 2nd, and 3rd
choices.