LH flights FRA-ZRH (my usual route) are usually covered with a slew of codes as well. I was recently on a CRJ that carried AC, UA, NH, BD, LX and RG codes besides the usual LH.

From what I could tell, the codeshare was in some measure of demand - I noticed UA, AC and RG boarding passes among my fellow pax, and my seatmate was booked on the LX codeshare with a connecting LX flight to JNB.