I've been wondering about this for a while, and I've come to the conclusion that blackberries are probably the original thing. Brambles grow like weeds all over Europe, I don't think anyone is cultivating them to be different. Apples definitely have had a human hand in selecting the best apples to start fresh orchards with.
I'm open to correction though.
If they had paid for use of the wall it would be very easy for them to prove it's not vandalism. They've never said they had permission, that I'm aware of. Can you link to them saying they do?