When I was over there (1993-1999), I heard lots of stories like that, of how there were tanks and other equipment just buried. Of many underground bunkers and floors of buildings that were buried, blown up or access denied to the lower buildings. I don't know if I blame the gov't for getting rid of the bunkers and such, as a historian I hate it, but if you have to deal with the legalities of people getting hurt, people wanting to explore and the chance to just fill it in and never worry about it again.
On the other hand, I have gone into bunkers and explored many WW2 places while over there that are still accessible. Some areas I could not go into very deep, as they were filled in and it always made me wonder what was beyond that wall. I went into some bunkers on the coast of the Netherlands and it was interesting to see the signs, in German to stay out and the bunkers # / designation.
Here are some pictures of some tank traps near Aachen Germany I took this last spring.
There are still areas where these run and you feel part of history. Most have been taken out by farmers, and the local gov't simply because of the room they take up.
Also, every year you still hear about bombs being discovered when a building is being built, the bomb squad comes in and blows it in place or takes it away.