Do iOS Contacts work with Prius car navigation systems?
BT Phone/Address systems use different Bluetooth "Stacks" or APIs. You have to check compatibility for each one at the mobile vendor's site or through third party enthusiast sites. Sadly, this level of detail is often beyond your average auto parts department because as an extension of sales they will simply say, "Yah, sure. It's Bluetooth, it'll work." For example our 2005 Prius could not speak Apple Address Bluetooth, but our 2012 Chrysler can.

Sadly, you won't get much milage (pardon the pun) out of hacks and jailbreaks because it comes down to the low level Bluetooth (sometimes at the chip level) that the equipment uses.

Also, to be an iOS compatible BT device, the device has to go thru the process of MFI certification.

So, again. you'll have to call your auto support line and in the case of the Prius; prepare for disappointment.

In the case where you have been able to exchange address book entries, you will likely need to make sure that the address book entry is in the right format. (Country, state, label, etc) Again... check with expert forums on that.

In the case of a Prius, I stongly recommend: PriusChat