Is this (planned) setup going to use Cisco equipment, or this a general question about
setting up a VPN?
Off the top of my head, it's easy enough to set up a site to site using the same private
IP addresses on either end -- case in point,
here's an example using Cisco-specific equipment.
Second part of your question, not sure what, if anything, it has to do with the site
to site you're trying to setup. Can you clarify at all?
Regards