Not being a pilot myself, but I would suspect the flight crew to be extra vigilant as to where the fuel is during a one-engine out situation (I know you have other things to look at, too...
).
Secondly, wasnīt there a "FUEL - wing tank imbalance" warning if the l/h and r/h inner tk fuel quantity differs by a certain quantitiy (3t?)?
Thirdly, I am very sure that the A330/A340 (classics at least) will give you a L/H (R/H) wing tk low level warning. Should leave enough time to reconfigure the fuel supply to the remaining engine.
(A3456 used to be different, see Virginīs diversion into AMS a few years ago).
Finally a question to the operating crews: I seem to remember that in case of a crossfeed valve failed closed, the procedure said to push the outer-to-inner tk xfer p/b, and to "slip" the a/c with one wing down (thus initiating gravity xfer through the refuel gallery).
Has anyone done this in flight? What were the xfer rates??
Cheers, J.V.