[ken1784]

Also, where would the Intelligent Parking Assist button be located in the Japanese Prius?

The main switch for the IPA is located at the left(+underneath) of the steering wheel.
There are spare slots as you can find. We, in Japan, can order some "Dealer Option" ("Port Option" in the US?).
So, they will install some switches there for such options...
http://www.toyota.jp/dop-prius/functional.html
(Japanese language only)

Regards,
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