That makes me kind of ambivalent about this undertaking :) But I also understand that for the Deutsche Bahn this means substantial damage and costs. On the other hand, more effective enforcement is probably mostly going to result in a larger ratio of quick-n-dirty tags, making the overall appearance messier, uglier and more vandalised.
Now I don't think that people should just be able to paint their murals on whatever property they don't own. That's not right. I just think it won't really change the appearance for the better.
I also don't like drones, btw. Flying surveillance robots? Brrr. At least ED-209 couldn't climb stairs ...