As Tommy says it is the same and interchangeable.
A few things have different sizes though across models (eg. the anti roll bar (and therefore bushes too) have different diameters on some RS200 of certain age or from sport to le to IS300 etc). For example my 2000 reg RS200 has 15mm but some are 14mm.
Also saw a post once with photo showing an Altezza front ball joint next to an IS200 one and the Altezza one was bigger but I think both actually fit?!
So yeah, same suspension really but be wary you get exactly the right spec of things/measure where unsure