Curious
Not sure what the real reason is/was for the tech stop in AMS. The story started by saying that the Virgin aircraft was having engine problems. To me that would require an extensive hangar visit before you would attempt to get it back to base. And it would make sense for Virgin to bring in another aircraft to get the people moving.
As for the toweless trucks go. The ones KLM uses for widebodies look strong enough to move an office building. They move the 747's around like they were toys, and I know this from extensive personal experience.
And as far as I know the 747 is still the heaviest baby on the block. So I could not think of one possible reason why they could not be used for the A340-600. If you were to divert to any airport in Europe I could not think of a better equiped place to do so than Schiphol. It can accomodate any sized aircraft, and the maintenance facilities there are top rate. A one stop shop.