In message , John Rowland
writes

I suspect the branch got caught between the bus and the tree-protection
rail and the branch/tree was pulled over by the bus.

I saw a picture in one of the free papers today (probably Metro) that
clearly shows part of a branch wedged in exactly that position, stuck
between the nearside protection rail and the body of the bus. It looked
very much like the other half of the branch that was pictured on the
roadway.

--
Paul Terry