No one knows for sure yet. Doesn't mean I can't speculate
If everything proceeds as planned, production will start on the 16th, slowly. It will ramp up over a couple of weeks time. Some of the line operators have said they can do 500 cars per shift.
As for the overwhelming amount of SS's ordered the first few weeks... Fbodfather has said that should not be an issue, the only issue would have been if the percentage of SS cars stayed at +75% for the duration. Initially GM had figured on a 50/50 split for the first few quarters, knowing full well that early pre-orders would go in favor of the SS cars.
As far as when... we have started to compare order numbers on some of the other sites, and it looks as though the alpha numeric order numbers are going in sequence. Whether or not you get your car before someone who ordered a few days before you, is anybody's guess. Orders could go in sequence, by trim level, color, region, just no way of knowing.
I ordered a 2SS/RS on Oct. 20th, again assuming that GM's money issues don't get any worse, with my above reasoning I am guessing I will take delivery sometime in April.
Hope that helps a little