yeah the correct term i beleive is the Opposition set Vol.1 and as you can see the main difference is the winter camouflage.
If you check the Konami site youll see it for sale Y12800. and its apparently a limited production.
There are a few sights on the net that will sell these sets.. approx $150 USD i came across a Japanese site that specilises in exporting anythign of interest to those of us not lucky enough to live in Japan. Ill be making an order for 2 of these sets tomorrow... for some reason theyll discount the sets to Y12200 however there is a handling fee...
i think if your interested in getting some of the field structures.. and atleast a pair of tanks.. the Opposition set is the way to go.