Here in Paris, Amex pays for reservations at some really difficult to book restaurants daily. In general the restaurant keeps the table until midday then releases it. Happens at many of the top Michelin starred hotel tables as well as high demand places like Jules Verne in the Eiffel Tower.

They can't do much for restaurants with a one year waiting list two weeks before .... Japan is very particular as well and most top places won't take "non-Japanese" without an invitation from a valued client or special chef contact.