Yes, I would suggest the junction box is for a heat tape that will be in the downspout to prevent freeze ups in winter (and on a GFI circuit). Assume it will be finished prior to that. Having done a lot of exterior structural and construction work on commercial buildings in the past, older buildings like this are not designed with deep enough sidewalks. The blocks are placed to stop vehicles from hitting the structure, as well as people on the sidewalk, plus to provide full use of the walk. Putting the blocks against the sidewalk would do nothing to prevent this. What your plan shows is merely a concept.
I could look into it, but I can't remember any specific building code criteria for the blocks. There definitely are code requirements now for new builds with regards to accessibility and clearances. Older buildings don't have to upgrade unless there is a major revision to the building.
You could 'lawyer up' and look at claiming against the property, but I think it would be an exercise in futility. No harm in asking though, you could get an opinion from one.