A first test was undertaken in 2010 at the FoAM Amsterdam garden. The garden also features 11 scion propagating trees, pear, apple and plum, from which cuttings can be placed on wild trees and shrubs in Amsterdam.
In 2012 one of the grafts sprouted some 7 remarkable apples, with an exceptional cinnamon / juniper taste, which deserves to be grown as a new variety. The worlds first guerrilla grafted apple variety has been named Rough Sloterdijk: https://fo.am/blog/2012/11/06/rough-sloterdijk/
see also: project groworld