Spitoon - I understand (para 4.5) that any significant depletion would be notified to pilots. I'm sure that anything affecting the category of cover offered would be considered significant and therefore would always be broadcast. Individual policies would be in specific aerodrome manuals, which is sensible because LHR would presumably want different rules than Bristol or somewhere.
In my case, we diverted because we were informed of the depletion at 2nm final, 100' above MDA. No discussion time so we flew the go-around and then only had fuel to divert. Our ops manual allows landing with RFFS 2 categories below the normal required, if it's due to a temporary, unforeseen depletion, so insurance is not an issue. In hindsight, we could have continued the approach and landed, but the manual wording isn't clear and the I don't remember the controller offering us the option of continuing, hence the divert!
Lastly, if no one informs you of a depletion, there is no case to answer as a pilot, since it's the aerodrome authority's responsibility to manage that part.