Matt,
AFAIK - what you are describing is layer 2 tunneling, providing layer 2 networks from two speperate locations.
The only way I am aware of how to provide this - does NOT invlove ASA's or VPN's suing layer 3. You could do this over MPLS or a transparent layer 2 pt-pt circuit.
Perhaps another netpro has done this or knows how - I did hear of someone bridging thru a GRE tunnel, not sure if that is a viable option or actually works.
HTH>