I've tried on several props, and matposes are not applied. This may be a Poser 8 issue -- within Poser 8 I can't apply mats to props by clicking on the icon in the library, but only by dragging the icon to the prop. (And, oddly enough, only if the prop isn't already selected.)
I had no problem applying mat poses to props.
Without a cr2 in the scene, props don't take mat poses, did you have a real cr2 figure in the scene?
Yes, I did have a real figure. I think it may be a Poser 8 issue, because some other people were having problems applying matposes to props by double clicking. I wonder if the bug (IIRC it was admitted as something that was broken between the beta and the gold) occurs downstream of where ACL interfaces.
There's been a bug when sending path information to Poser, the latest beta should have fixed that, so it should be as bad as Poser's file loading. Please tell me, if that's true for your mat poses.