A quick grep for "cursor_type" reveals that it's only mentioned in options/find.X, never in any of the implementation files. So, we just don't propagate it and there's no way to ask for a tailable or await cursor right now.

Mentioned in the mongodb-dev group at:
https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/mongodb-user/Q1ZdZBnVOIg/85DFEB_YFgAJ