Oldlae,
Ops across the Siberian areas are not as precise as you seem to think they are. The loadsheet (and therefore calculated fuel burn) is provisional based on all male pax and predicted cargo. The final loadsheet is recieved after pushback and contains actual cargo and a Male / Female split therefore the final figures are usually a few tonnes less than the provisional figures. The flightplan fuel burn is derived from the provisional weights and ANTICIPATED atc altitude clearances (remember Siberia is metric non rvsm so there are large differences between available levels). If the crew are able to negotiate more efficient clearances enroute more fuel savings can be made. Also if the crew are able to negotiate better levels enroute the wind may also be more in their favour. All this for 10+ hours flight.
My point is that if all factors go the crews way it is not unusual to land with a few tonnes more fuel than planned. Likewise if all factors go against the crew they will have to use some or all of their contingency fuel. That's what it's there for.
Those of you that think it's significant that BA038 used less fuel than anticipated to get to LHR or that fuel quantity indications were innacurate are barking up the wrong tree.
LD