Just heard about a presentation by Airbus re a software flight planning tool that predicts fuel temps in the tanks of the 340-500/600 for the trans polar routes. This can be built in to the CFP to give an accurate prediction of where the tank temps will be at their coldest and how to get around the problem.
Apparently going from HKG/SIN/DXB etc to the USA is no problem because the fuel being used is Jet A1, but on the return leg with Jet A in the tanks there can be some restrictions. Interestingly one technique (as I understand it) is to keep some of the fuel in the centre (warmer..cos it has not been exposed to the cold outside air) tanks and then transfer it to the coldest wing tanks...typically the outboard mains...to keep them above the freeze point.
Another technique being used is to freeze an actual fuel sample of the fuel loaded and then ACARS the crew after departure with the actual freeze point which can be significantly different from spec so the crew can take appropriate action.
Apparently sometimes if the fuel were to get real cold, descending to try and get a higher OAT and thus more skin friction heating is not going to work because of a the cold air 'bubble' that is found in the middle altitudes over the poles.
So yes cold fuel is an issue in today's environment but only for the extra long range types.