OK. Per our Kronos Totalizer advisor and occasional blog poster DG, as of 5.2 there is no longer any such thing as a Callable Totalizer Engine. The so-called Callable Totalizer (CT) was an artifact of the Smalltalk implementation of the totalizer in 5.1 and earlier. From 5.2 onwards, all on-the-fly totalization goes through the same (multithreaded) totalizer servlet stuff.
The CT still exists, in the sense that it wraps core totalization with accruals and other secondary computations. That's why it's used by the accruals package as well as WAT. It's a focal point in the logic, rather than a throttling point for performance.
There are also a few errors that appear to be attributed to the CT such a:
"WTK-032554 Callable Totalizer system error: Could not find item to delete", but this seems to be an Audit trail error rather than the fault of the remnants of the CT.
In WFC.log "TotalizerProcessingException: Your connection to the Callable Totalizer has been lost. Please refresh your timecard." But this is a time zone error that the totalizer is freaking out about.
I KNOW there is more to say about this stuff. I'd love for you to add your 2 cents to the comments on this one.