Hi apologies for reviving a 4 years dead thread. Better late than never, I'm sure someone in the future might be looking for info on this. I myself was looking for documentation (which doesn't exist as of writing) and did some trial and error to test this.
The slave does work, but it's a bit unusual. Let me explain-
While the basic modes of the ATLS-TRC slave work just fine in route mode,
LCM mode does not work properly at all. This is because the ATLS-TRC slave is not able to delete the invisible train, resulting in the crossing becoming permanently stuck closed. To prevent this, it needs a bit of a push from ATLS.
You can do this by adding an ATLS controller in Route mode. Add 2 routes and 2 phases as seen in the attached picture. Set route 1 to green and minimize the timings. These are the intervals where the ATLS system will attempt to clear the invisible train. Assuming your train is still keeping the normal TRC stuff active, it will not delete the invisible train.
Next, name the ATLS-TRC slave in accordance with your TRC crossing (e.g. 1&3, 2&1, etc). You should also set your channel and set the slave to Route 1.
A minor impact of this system is that it can take up to 5 additional seconds for the crossing to open after your train is cleared. Aside from that, the system works quite well in my opinion.