Sorry for the late reply, my latest month has been roller coaster from jetlag management, and June seems to be the same. @bblacey, we will be on the same timezone
Regarding the TBB support into OCCT, it has been introduced by OpenCascade to accelerate some operation like Compound computation which are done in parallel now on multicore chip (look at you CPU load when computing large Compound). This is also useful during the STEP reading operation.
We used TBB as an initial parallel library, there was some debates about OpenMP, or any other higher level library than standard PThreads. TBB is coming from Intel, and is "open". I am not a big fan of it, but it does the job currently.