If that is true it seems like very bad marketing. The songs from the "limited" version will be out there for everyone to download before they even have a chance to buy a CD.
The limited version could leak if the version in the magazine is sold seperately, but otherwise it would be hard to leak. In Motorhead's case the CD may not contain any bonus tracks at all yet as I haven't seen anything supporting this.
The Slash version is a good example to the no leak theory, it didn't hit download sites until the magazine hit the shops, and I haven't seen many magazine boxes go missing from warehouses before their release.