Index: src/engine.cpp
===================================================================
--- src/engine.cpp	(revision 27595)
+++ src/engine.cpp	(working copy)
@@ -902,7 +902,7 @@
 CommandCost CmdWantEnginePreview(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
 {
 	Engine *e = Engine::GetIfValid(p1);
-	if (e == NULL || e->preview_company != _current_company) return CMD_ERROR;
+	if (e == NULL || !(e->flags & ENGINE_EXCLUSIVE_PREVIEW) || e->preview_company != _current_company) return CMD_ERROR;
 
 	if (flags & DC_EXEC) AcceptEnginePreview(p1, _current_company);