Mostly know as "Hit the Dirt!".
Mortars are good, lmgs from longrange (a squad behind the rushed one), HMGs with Incendary rounds tear them apart because the don't get the damagereduction surpressed units normally get. Flameweopons work great too. Scoutcars from maxrange too. Snipers could be OK.
Or you can crush them with tanks, because they don't move. This works so good (if you have a tank).
+1. Also know that the conscripts cannot retreat for a few seconds after they have used Hit the Dirt. This makes them very vulnerable to any kind of grenade, if you can get it off immediately. Good players will not use HtD until their conscripts are a little spread out, however, which minimizes the effectiveness of grenades.