Those crafty Russians also considered that possibility during the Great Patriotic War. That's why they had blocking battalions. Either you charged against the Germans or you're summarily executed by the blocking battalions if you take one step back. No reason they couldn't revive them.
Note: Blocking battalions were used against all Russian soldiers, not just those in penal battalions.
Being invaded is a different situation than invading. Also it was the Great Patriotic War. This one is just expansion. And with modern communications, a prisoner brigade could easily call the other side, and that “charge” could quickly turn into “join”.