OK, I got a reply from Takayama city saying some buses are accessible, others aren’t.  Not terribly helpful.

However, they gave me the phone number for the bus operator, Nohi Bus.  I called them and the bus to Shirakawa-Go is definitely not accessible.  The only option would be for people who can fold their wheelchair and walk up the steps. … Read more

@joanp was the train from Nagoya to Takayama a reserved seating train (ie would need to book the accessible seat in advance), or just a regular train?

Hi @Jiru

I know of one place in Osaka, but don’t really want to post their email on here without their consent.  I have sent you  friend request.  Once you accept the friend request I’ll send you the info via a private message 🙂

Sorry for all the emails!

I sent an email to Takayama city about the accessibility of the local buses.  It is a holiday here until tuesday, so it may be a while before I get a reply.

This wheelchair taxi company offers a tour of the main locations for 24,700 yen.  http://www.kaigo-taxi-hiyoko.com/kannkoumoderuko-su.html

@joanp , you went to Shirakawa-go, right?  How was wheelchair accessin that area?