When you perform the initial pairing of the phone to the Bluetooth hands free system, it will automatically synchronize the address book, however, many phones that include the Treo's, and mostly Verizon phones will not automatically synchronize.
This is no fault of the Lexus system, but it lies in the phone and/or carrier. You can manually enter the contacts via object push on your phone, once they are in...they are in! Also, sometimes the address book will just synchronize by itself as it did for me one day. It's crazy that many Verizon phones don't synchronize, but it's because Verizon is trying to drive customers to become subscribers to other services they offer, such as their picture service. For example, Parrot has a Bluetooth picture frame where you can wirelessly send your camera phone pictures to, however, Verizon phones typically do not work, since they tweeked the Bluetooth by adding a buffer if I am not mistaken. Hope this helps!