Sorry, you can't use the strat cities as "clutter" for GVs. HTC have told me there are issues with putting extra copies of these cities or the even individual parts of them into MA maps for GVs to fight in. The issues are to do with auto AA and strat resupply, basically they are tied into the arena in a way that you can't get rid of in the TE.
IIRC the three or six main strat cities on an MA terrain have to be placed well behind the front line to prevent them getting bombed too easily. I'm not sure but I think I read HTC don't want any GV spawns into them either. Best to check with them before doing so. I believe your only option for some extra urban sprawl at the moment is to use the tanktown object in the TE.