Beta 4 has added the following issue.
You cannot place streetlights (any variation) on sidewalk tiles on level -1 or -2
HOWEVER - you can place them on the bus/taxi/car sidewalk tiles that are part of those elements. And they work fine on level 0 in any location like they are supposed to
ALSO- GLITCH! On level -1 or -2 if you place a trashcan first on the sidewalk, you can place the streetlight on that same tile. Then you have a trashcan and streetlight on the same tile.
Maybe this is some sort of tile saving algorithm or something.
Happy Turkey Day!