Pam @pamknowler has it right, they're smoking spliffs... maybe the poster is meant to indicate that it is an area frequented by dealers - a pair of old trainers thrown over an overhead wire has the same signification.
@vignouse@pamknowler Oh, what an innocent I am. I should have realised! I suspect there's a bit of that goes on in parts of Belleville! My 'old trainer' photo of a few weeks back stacks up with that - similar part of town!
A cool shot and I had to smile at the comments. When I first viewed the image my eyes were drawn to their faces and not so much what they were smoking. After reading Pam's comment I took a closer look at what they were smoking and of course it appeared quite obvious then. Yes, they do look a bit stoned. :-)