Using an empty foreign construction plot "just like that".

I was at our empty building plots today and was amazed to find that the entire site was full of (heavy-duty) vehicles. Next door, a prefabricated house was being erected and all the vehicles that were probably involved with the construction were parked on our property.

Of course, they couldn’t ask anyone, there is no nameplate on the property. It doesn’t really bother me in principle, unless damage occurs. That’s why I photographed the currently still intact shafts as well as the vehicles with license plates.

My question: Does driving on the property alone cause any later disadvantage/damage? (Keyword compaction). If not, are they allowed to stay there as long as they want? Otherwise: How should one proceed? Other parking options for the vehicles are very difficult.

Live and let live. Just insist that they clean up their trash afterwards.

was also my first thought,

I only have concerns because of my recent experiences with the topic of construction
fearing damage to suffer that I have to pay for without having caused it.
No, you can't call it fear, rather doubts, worries?
Whatever.

Of course, it is easier that way. But in principle, they should have managed it even if your house had already been standing there. And then what?

I would talk to the future neighbor and say that it doesn't bother you in principle, as long as it doesn't cause you any harm and any traces are removed again. If it turns out that you have suffered damage because of it (compaction or God knows what), you will report it and assume that your future neighbor will certainly be responsible for it.

Politely, because he will be your neighbor after all, you don't want to wake sleeping dogs, but as I said, it is a bit cheeky to just occupy the property there for the sake of simplifying your own construction activities.
If no damage has occurred to you now, let bygones be bygones. But I don't find it very nice at all if no permission was obtained in advance.

I can understand that, I would also be worried that this might cause a (financial) disadvantage for me. I also think it is best to talk to the neighbor. Depending on how they react, you can then take action (either let everything continue as is or prohibit use).

Don't worry, you won't really have any damage. Compaction doesn't really matter, because everything will be dug up again anyway when the outdoor facilities are due. Just make sure your shafts stay intact (also open the lids sometimes to check that the concrete rings and the cone have no cracks). Otherwise, not much can really happen. When you're ready, you can also use some neighborhood help. For example, your neighbor could return the favor with construction electricity or water... That way, everyone has a little advantage.