Yeah then if Google doesn't offer this as a service, I would think your only option is to get a server of your own (either in-house or hosted), and use Exchange, or something like exchange.
http://technet.microsoft.com/en-us/library/aa997525.aspx
O
ther than the "multiple entry points" I suggested earlier, I don't believe there is another way to emails go to multiple places. You need to have full control over the operations of the server that is hosting your email (like exchange).