Sorry Martin, just got back last night and can now update you. You must leave your UHF radios at home unfortunately

The simple solution to stay in touch in Myoko is to use 3G mobile phones with international roaming or
you can easily hire phones cheaply through Mobell (link). SMS text messages also work very well.
The Japanese Government has ruled, quite reasonably, that Australian UHF-CB radios cannot be used in Japan because they may interfere with radio communications related to disaster prevention. Australian UHF-CB radios also use the frequency band used for television broadcasting in Japan.
If you possess non-conforming radio equipment in a condition where a signal can be emitted, you will be considered to have established an illegal radio station, regardless of whether you are aware of the illegality or even whether you have used the radio equipment.
Strict penalties apply and the warning details are
here (link). It's also suggests that the authorities may get tougher on this issue next season.
So unless you want to stay in Japan for a full year (on an involuntary basis), or have a million yen you no longer need, better leave your UHF-CB radios in Australia.
This is also discussed on a
Niseko blog here
Cheers, MG
Reference