IIRC, the npc spawn command does not work in mutliplayer. However, if your goal is to have these NPCs usable in multiplayer maps, you CAN load multiplayer maps into singleplayer.
To do that, start up multiplayer and bring down the console (**** ~). Then type "map <mapname>". This will load the desired map. Once you do that, you can spawn any of the NPCs. I have set up my own config file so that by hitting the F1-F12 keys, it spawns different NPCs to fight. You can even spawn the Jedi apprentice, Luke, etc. and they fight along side you. Pretty cool.
Hope that helps...