why not? Put the head of the HAT Russian dragoons on them and you have Russian cavalry for Eylau. Or give them a Czapka and another hand with a lance. The greatcoat was the same style in 1812 as in 1855.
Just wanted to agree that they would work well (with head swaps) for Russians, as was mentioned. For Prussians, though, I'm not so sure. The greatcoat that the Russians used is longer than the litewka that the Prussians used. Also, the set has oilcloth covers for the shakos, (which is good) but they are covering a differently shaped shako than what the Prussians used almost forty years before.
Still, it might be a matter of personal choice. Just use different horses.