Leewan,
Its would be interesting to know what kind of scenario are you looking for???
Every PCU for all the flight controls have Back-ups meaning they are powered by 2 systems at 1 time, so if you lose either system, there is always control of the a/c.
Redundancy is also there as explained above, and also within the computers which controls them,
Then you have Check valves in the systems if you have any leaks of some sorts.....
But I cant figure out what kind of scenario are you looking at????
I know when Boeing(or Airbus) comes up with any design they have to satisfy all the scenarios to FAA/ or EASA for any eventualities, and then only the Type Certificate is issued. So I am sure most of it should have been covered.......except the ''Finger Trouble of the Crew''
( sorry no offenses to anyone) !!!!