Have a look at Alex Mikaberidze's Borodino OOB for the French here: http://www.napoleon-series.org/military/battles/1812/Russia/Borodino/Mikaberidze/OrdersofBattle/c_MikaberidzeOOB2.html. The 12th Uhlans are shown as part of the Corps Cavalry for Poniatowski's V Corps, whilst the 3rd, 15th, and 16th Uhlans make up a brigade of the IV Reserve Cavalry Corps (towards the bottom of the page).