^ What Tordanik said. They are two distinct objects and should be mapped as such.
The entrance example actually illustrates that point. The entrance node is a separate entity from the building way itself and has different tags, etc… Their relation to each is implicitly expressed by the entrance node being part of the way.
Now, the problem we are facing here with the bin and the street lamp is that there is no way to express this implicit relation between two nodes like we can between a node and a way. However, that should not fundamentally change the way we map the objects themselves. We just need a different way to express the relation between them.
Consider the following: If the street lamp was mapped as a way, would you still add tags for the bin to the lamp object itself? Or would you just add the bin as a separate node joined to the way (like the entrance node on a building)? Why should this be different if the lamp was a node instead?