On windows adminshell doesn't read script if supplied on stdin. It looks like it is reading from terminal (unlike adminshell on linux). I see that one can supply expression as first argument to adminshell but it seems to accept only a single expression and additionally complex expressions are a hell to escape properly.

Assuming adminshell is intended to be used for automating administrative tasks, it needs a straightforward way to execute scripts non-interactively so current behavior on windows needs to be fixed.