It is put in the legislation to expand information access. The way it should work is that people follow the legislation—departments, the PBO—and information flows, and there is no issue. That should happen 99% of the time.
In areas where there is a dispute, there should be an attempt to work it out. If it can't be worked out, the PBO does have significant recourse through Parliament, and that's the best place for it to go, not through the courts. You want your PBO focused on economics; you don't want him focused on legal procedures.
That would be my advice.