Usually - but if you have something with a custom morph (made with magnets or a 3d modeller) that has been made into an injection pose then there probably will be a set of files that don't go in the Pose library, as they aren't intended to be used directly but are instead called by the Inj/Rem poses. That's why it's a good idea to unzip with path names, even if you do it to a temporary folder. However the basic Inj/rem poses that are visible to the user within Poser can be moved around like Mat files, yes.