The two Vk 3001 vehicles were shipped to southern Russia and saw action with 16th Panzer until lost. They were nicknamed die Sture Emils (sort of a German version of the English Ugly Duckling) while the two Pz sfl IVa went to 3rd Panzer with AGC. These by most accounts operated until their unique ammuntion ran out at which point they were shipped back to Germany. I am not aware of what their ultimate fate was.