I've heard of this...and while I love the idea of planting something where ever you can, in my opinion, the idea of taking something that should be recycled and using it in a way that some call recycling but in fact turns it ultimitely into trash is not a sound one. My understanding is that weathered plastic bottles can't be recycled....and plastics as they break down can leach out bad things.
"We're all just walking each other home." -Ram Dass
"Be a lamp, or a lifeboat, or a ladder."-Rumi