Moondog reminded me of something from a while back. A few years ago (2006 i recall) in Beijing, there was a story of a fake cab who killed passengers for organs. Heard about it via embassy staff who had to get the bodies, gov't (of course) kept it hush hush, definetly didn't make news. Wasn't a black cab but a disguised fake cab. It looked exactly like a metered cab, but didn't have the 京B plate.

In terms of the shanghai tunnels, there are certain hours of the day that cabs aren't allowed to use them. That doesn't mean that they won't try the grand tour of the city on the newbie 老外 trying to find 外坛.