I was on vacation last week (and spent a little time at WDW).  I went to the MK only on 10/3 for MNSSHP and the walls hadn't been put up yet, so I suspect it happened just a few days later.

Anywho, fellow Doombug Ricky does have a story on this up on his site, and there's been speculation and discussion on various Disney boards as to how interactive this queue will be.  Only time will tell.

http://www.insidethemagic.net/2010/10/cryptic-changes-underway-at-walt-disney-worlds-haunted-mansion-graveyard-interactivity-rumored/

According to a few "insiders" on other boards, the queue won't be interactive along the lines of Space Mountain or parts of Spaceship Earth, and the tombstones won't be taken away from the area, just relocated.  Regardless of what's done, I'm curious to see how it turns out.  Hopefully it'll be a change for the better.