What an interesting idea!
When planning urban spaces such as an underground station, two major questions are always present: route planning and turning a no-space into a space.
Route planning is the study of the routes people take/should take in a space (think about an exhibition gallery as a sort of a classical case, though actually route planning should go to such detail as routing inside a house, or a kitchen). An underground station is a paramount problem: you have thousands of people circuiting there everyday. They need to be able to orient themselves (sense of orientation drops amazingly below ground); they need to be able to go quickly inside the station; they need – very importantly – to be able to escape even more quickly in case of accident or fire. In this last case, security measures may force electrical devices such as elevators, escalators, etc, to shut down – this can cause confusion and delay if people try to use them to escape. So something that trains people into preferring stairs to electric devices as their usual route can be very positive.
As for the no-space thingy, well, we all know what it is. It is that uncomfy feeling everyone gets at many public spaces: a place which, belonging to everyone, belongs to nobody simultaneously. Too large, too unreferenced, too confusing… also, sadly so oftenly: too shabby, too uncared for, too full of grafitti! Interventions like this can help turn a no-space into a space, since people can appropriate the intervention for a bit, make it theirs.
I suddenly thought that a lot of SL spaces are no-spaces. Interesting, why should that be?