As I can guess by exploring CK menus, when you try to change footstep sounds - you actually can define which sound should be played depending on matherial player is standing on AND the footgear player is wearing... I mean it's more than just simple NIF associated sound somewhere deep in the game engine. So in theory it should be possible to extract some info about which NIF (or anything) the player is on. And it would be a shame if there's simply no API present in Papyrus to get that information, though. :\
Seems like the only information about player's position we can easily get in script contains of current cell ID, current worldspace.. and the raw coordinates, I guess. Which is definitely not enough for a script, where something should happen when the player walks onto slippery ice, for example.