When I finished my bombing run (in a completely empty Undercity), I pressed Return Home, and it went on cooldown and played the spell animation, but the woman piloting my broomstick is currently spiriting me across the Eastern Kingdoms. I think she may be taking me to Stormwind via the scenic route. Directly through mountains, fatigue zones, water hazards, and walls.
EDIT: Oh, she kept going. I escaped via queuing for Headless Horseman.