The answer is yes, but it's not easy, and you should probably have a hybrid qualified dealer do it.

I was told in 2005 that there is one data cable, that either goes to the green message center box, or the navigation unit. IE not both at the same time.

I heard of one person who had a defective dashboard instrument, and when the dealer returned his car, he had MPG on both the green message center AND the Navigation screen at the same time. So who knows? But I'm pretty sure it is possible. Make sure you get a great price for the Ford Hybrid NAV, so you can pay for the dealer to install it.

-John