I am in agreement that neighbors need to maintain the alley area adjacent to their property.  Likewise, it is the responsibility of the owner to maintain easement areas adjacent to their property also.  That includes easements that are grass areas even though it may not be paved.  I believe that it is a city ordinance requiring property owners to properly maintain easements/alleys.

this tree sat on the back side of my property, approximately three feet up off alley level.  cannot imagine whose vehicle would be damged by that tree...or any of the plants growing to keep the soil from washing away.  if city vehicles and other large trucks, et al, hadn't been ramming into the concrete blocks holding up that part of the property over the years, all would be well enough.  i have lived here over twenty-seven years and never had a problem before this.  if anyone had trouble getting past anyone's foliage, the polite thing to do would be to leave a written request for that homeowner's assistance, not jts tear things up and out.  it's tacky, like mowing your front yard and leaving the cut grass laying in the sidewalk to wash down into the storm drains.

 Very good msm, property owners are to maintain property in front of their homes out to the curb as well.  It dosen't stop at the end of their sidewalk.