The Network Manager applet is patched to expose the org.openxt.nmapplet interface but does so by registering its service name as org.openxt, the top level namespace for OpenXT. This should be updated to register a unique name under the top level namespace, e.g. it could just use org.openxt.nmapplet.
In the NDVM:
dbus-send --system --print-reply --dest=org.freedesktop.DBus / org.freedesktop.DBus.GetConnectionUnixProcessID string:org.openxt
If it returns an integer (which should be dbus-bouncer), then nmapplet is using the service name