ThunarPlugger is a standalone application which is able to run a Thunar plugin
which provides a property page. The command

thunar-plugger <class-name> <path> [ <path> ...]

opens the dialog with the page described by a <class-name> passing the
remaining path options as arguments to the plugin. The class-name argument
is the hardcoded name of the GObject class providing the ThunarxPropertyPage
interface. To know it you probably have to look into the plugin code.