On a related note, I've noticed that when running Zerotier (virtual LAN over the Internet, free and nifty) my MBP sees the two servers I'm using as Time Machine

On a related note, I've noticed that when running Zerotier (virtual LAN over the Internet, free and nifty) my MBP sees the two servers I'm using as Time Machine destinations whenever it's connected to the Internet and performs backups to them remotely. Not necessarily a good thing when I'm tethering, but neat other times :P