Comment 40 for bug 895118

If you grind the Chrono Prison, you grind the Chrono Prison, thus you reverse engineer the Chrono Prison, and can build the Chrono Prison.
No handling for passengers of any kind was added yet.

Also, how are you going to force non-owned units directly into the Grinder?
You can only control them if you own them, one way or another.

iow: As far as I can tell from the bug report, everything is working as expected at this point.