Softimage 2013 SP1 included a fix for a problem (aka a crash) with the Simulate Bullet Rigid Bodies nodes and states.
So, when a customer asked us how to do a two-part simulation, I gave Bullet + States a try. In the first part, the objects drop onto an obstacle, and in the second part, another obstacle comes along and pushes some of the objects away. Like this:
Here’s the ICE tree. I used Test Current Frame to trigger the state change. I did try some other triggers, like Test Particle Velocity and Test Particle Size, but I got some weird results with those triggers. By weird, I mean things like some, but not all, of the small cylinders being pushed away, even though they were still in the first state.
The idea here is to push just the big cubes. I make all the little cubes passive, so they get left behind.
eX-SI 
What’s with the leftover cubes in the sim? Shouldn’t they be being pushed too?
Nope, the idea was to push just some of the cubes. For demo purposes, I based it on the size: I push the big cubes only (I made the little cubes passive in the second state)