I moved with the cart about 200m to lay road tiles - when accessing the cart's inventory i realized that i can access stockpiles that are 200m away. I can drag road tiles from this far-away stockpile into my wood cart.
The access to the far-away stockpiles doesn't happen anytime - i don't know which circumstances lead to this malfunction. It just seems, only the stockpiles are shown, that were in range, when i last looked into the cart (when i was on my property).
Edit: Also, it is possible to move items between the shown far away storage units (so from one stockpile to another or to a chest). This behaviour is just like being normal at the range of the storage units.