In terms of those who slip through the net it will likely be those that have been redistributed to smaller couriers, e.g, parcel express etc, from UPS or TNT if they don't cover the area. The reason these smaller firms will ship them out early is that it costs the courier company far more to keep a package than it does to store it. The likes of UPS/TNT will have the facility to
do this and use it in order to keep Apple sweet but the smaller ones will just want the package delivered and out of their hands. So, if your iPad has been passed to a third party courier, I reckon, you've got a good chance of getting it early.