Do you know how much changed for the sequels? From some reverse engineering, Crash Warped relies on depth bucketing for dynamic triangles, while level geometry is streamed from the disk based on the camera position, already at the appropriate LOD and sorted and bucketed. Is the BSP logic you're talking about real-time, or part of a similar pre-processing step?
We didn’t use BSP trees for Crash 1-3; instead we pre-rendered frames of the game on our SGI workstations and recovered the sort order from the (software) Z buffer. Then we stored the sorted list of polygons, using differential compression between key frames to reduce the space required. It was a total brute force hack.
What I think you’re seeing in Warped is what we did with Crash 1 and 2 as well: I had to sort the foreground object polygons into the pre-sorted background polygons. That was modified bucket sorting, but there were manually tuned adjustments to make it work and stable between frames.
