Does anyone have information on how Polish soldiers in the German army, whe...

In case you are thinking of a dramatic way being used by the Polish fighting alongside Germans once captured by the Allied forces, I found no such incident. So my guess is that the use of normal identity papers would have been the order of the day as the Germans always kept the Polish conscripts separate and easy to identify within their units. Before going to understand the loyalties of the Polish towards Germany and their fighting will for protection of Germany, there is a need to understand the history between Poland and Germany.
German Invasion of Poland and Conscription
Germany invaded Poland in 1939 and started forced conscription. As a result about 225,000 citizens of Poland were drafted into German Army. Despite such a large number of troops from a single territory, no Polish unit was ever formed in Germany and the Polish continued serving in Wehrmacht and Waffen SS. A number of notables in Germany proposed and supported the idea of a Polish Army to assist Germany in her war against Stalin but Hitler was never impressed.
For the Polish it became mandatory to sign Volksliste ("German People's List") and those who did not comply were deported to concentration camps. Any one who signed it was subsequently drafted into Army. It is highlighted that Germany was never sure about the fighting skills and devotion of Polish towards their cause as they had the historic abandoning of German and Austrian Armies in 1917 and 1918 to remind them. However, during their stalled offensive against Stalin, they tried to muster the support of volunteers by offering the command of one of the Division to a Polish General but the General declined the offer.
As a propaganda measure, German War Office introduced a number of offers and incentives to raise Polish volunteers but only 471 Poles came to get drafted. Approximately 69,000 Polish were capture by Britain alone after the end of World war in 1945. The ones that got captured by the Western nations were lucky somewhat as those captured in Russia faced extreme food shortage and disease and many perished.