I don't know if this has been figured out already, but its cools so I'll see if anyone knows about it.
I was trying to make it so scarabs wouldn't die with the set generic command point and patrol to location thing (by the way, I still cant get them to stop dying. But thats off topic) and I set
both the command point and patrol to location to the same location (preserve trigger + HT). When I moved the scarabs to another location, they spawned there, then started moving back to the generic command point/patrolling location.
Now, the neat thing is the location I moved the scarabs to was centered to a unit, and when I moved the unit the scarabs moved to the PLACE they spawned, not the location where the unit had moved. A note though: The location the generic command point and patrol to location has to be blocked off so the scarabs cant actually get there (e.g. surrounded by water or made of ice surrounded by snow).
You could (not practical) have hundreds of scarabs moving back-and-forth all in separate places with 3 locations. One location for the generic command point and patrolling, one for a unit to walk to, and one to center around that unit.
I havent tested it on other units yet, but I'm sure it will work. I dont see why not. Its pretty cool actually.
Heres the map I tested it on and the replay to show you what it looks like (if you cant get it to work). Unseige the tank to spawn a scarab where you are.
(don't mind the crappy map revealers )