This is a known issue. It just doesn't work.
Plan regions were originally more specific to Architectural models.
There was a fix in update 1 build 20090612_2115.
If I remember right, I think it worked correrctly for a short time until the release of the next update.
Anyway.
You'll have to come up with other work arounds to acheive your view results.
"It's hardware that makes a machine fast. It's software that makes a fast machine slow."