I remember that in metro LL that everybody claimed that D6 was untouched before the Rangers found it,but,if you take a close look in metro 2033,D6 had dead people in some rooms,and even ammo and guns.And one more thing,D6 had tanks in it in metro 2033,why,didn't the Rangers mount them and clear the city,or even escape the city somewhere???
Because there is no fuel, there is no way to get them to the surface or they are rusted through just like most other vehicles.
And i also doubt anyone would know how to use them you dont just jump in and hit the start button, Didnt D6 just turn out to be a giant Biological and chemical weapon depot?