Most modern aircraft have fire handles which shut off the fuel at the engine (FMU, HMU, etc) .... as well as at the fuel spar valve (usually in the wing). These include the 767, 747-400, 767NG, etc. This will result in a very quick shutdown.
I had to pull a 747-400 fire handle as part of a maintenance check last year. I reset the handle, but, at the time, I didn't realise that I would have to manually reset the associated generator field breaker (by cycling the GCB switches). Perhaps this is what ASFKAP refers to? Loss of all main bus power?
Rgds.
NSEU