YES ! Any of the 05 onwards BT/Assist TCUs share the same external antenna for Assist calls and Handset calls when the phone is using the cradle. They updated the wiring harness to accomodate this. If you look at your TCU you should see 3 antenna connections to the TCU. 1 goes to the external antenna. One goes to the BT antenna and one goes to the handset (for antenna signal) when used with a cradle.

The dealer is giving you the run around.

You already have everything you need in your 06 car, and so long as you can find a cradle which works with your handset you'll be all set.