No, it's nothing like MAC addresses. I'm not fully versed on the nitty gritty (I know just enough to be dangerous), but in a nutshell the Arduino IDE uploads compiled binaries to the Particle cloud, and the Oaks periodically check (every 15s?) for updates, and if there is one, they download it and apply it. So working across subnets should be fine... as long as both sides can talk to the internet... as they don't actually talk directly to one another.