I'm sure that someone will correct me if I'm wrong. But as I understand it, an LSD will help you put the power down when cornering hard. With an "open" (conventional) diff, the power could mostly be spun away through a lightly-loaded wheel due to the cornering forces, meaning you won't get the power down properly. A limited-slip diff will, as the name suggests, limit the slip that the diff produces which means that you can get more power down.
Traction control can work in different ways. On the IS200 it seems to work by detecting when the wheels are slipping and then limiting/cutting the power.
So the LSD helps you put more power down in some situations, whereas the IS200's electronic traction control will actual cut the power in other situations. So they'll be doing different things.
But yes, in a way the LSD is a sort of traction control.