Well, I mean move up from underneath, then launch assault.
Common sense still works best unless
GW has a rule saying it doesn't.
Just use the access points if your opponents say you can't levi-charge them like ruins. They are in the
RAW at least. I'm not even sure I would allow a floating move up to the top since it has access points. Only jet packs or skimmers could get off the edge or else I'd make you take a Leaping Down (p95) test.