Using this code below deletes the objects successfully, but the EDEN Editor icons remain and can be moved around;

{

if(typeOf _x == "Sign_Sphere25cm_F") then {
   deleteVehicle _x;
};

} forEach (all3DENEntities select 0);

And this doesn't work at all;
delete3DENEntities[all3DENEntities select 0, "Sign_Sphere25cm_F"];