THECORBYLOON, I think you'll find that the S of S was referring to fluctuation of temperature rather than a higher temperature.
Common sense would indeed seem to point to a reduction of efficacy of the vaccine if the storage temperature was reduced by -10 degrees C from that intended. However, this is not the case here. The efficacy is indeed reduced but by a very negligible amount that for all practical purposes can be ignored.
I chose not to discuss some issues over the containers provided by Pfizer but now it's become necessary. The long and short of it is that no portable container can maintain the same temperature as the ULT for hours/days on end. If they could, we wouldn't need the freezers as I can knock up in a lab a suitably enclosed freezing mix (see my answer above). In a nutshell, the container contents are regarded as viable and fine if upon unsealing, the vials are at -70 degrees C or colder.
I'm puzzled about your second paragraph. The vaccine returns to ULT storage when it enters the country of destination. The vaccine temperature can be raised at the immunisation centre by allowing the temperature to rise in a medical fridge or by other means. If long journeys are necessary within that host country then the Pfizer transportation container is redeployed but other equipment is available.