On any recent sales, if I go to 'order details' and 'print invoice' I can see the buyer's registration address (which I would assume is also the billing address) in the top right hand corner of the invoice and the shipping address in the left hand corner.

Frequently they are both the same but in some cases the name and address are completely different.

So, yes, sellers have access to both addresses (if they are different) whether it's a Simple Delivery sale or the item has been sent with custom postage.