To your point, I would say that the machinery has a negligible impact compared to the benefits of permaculture, and if makes permaculture more productive without greater risk, then it seems good. That is, we shouldn't have some kind of Luddite purist view of permaculture - it should be practicable. Things like this help to break the stereotype that permaculture is just hippies chanting in a field that conventional agriculture proponents seem to believe and do perpetuate.
Affirmative, use the best tools for your context, especially when those tools were used to destroy the natural system that used to be there. (My land was filled with stone and gravel with 4-6 inches of soil ontop using machines...)
Use any means nessasary to move the current system into one that will self-renew and self replicate.
That's permaculture. Set into motion a permanent self-renewing system!
