Need help on Takayama to Shirakawa trip

So,the rail between toyama and takayama is down,and i need to use the hokuriku pass to travel from takayama back to kanazawa. I asked the railroad bus staff and they booked for me a seat on the shirakawa to kanazawa trip,and said that I can get on a local bus for my takayama to kanazawa trip,and its covered by my bus. I just want to ask if this is completely correct? Because I'm confused by what buses need reservations and which ones don't need. Thanks.

by Zedwye