I booked a LH/AI combo MUC-FRA-DEL-CCU last week on AI stock and the TA has sent me a PDF confirmation generated from Amadeus with 2D codes added on every segemnt on the confirmation
Lets see how the CISF will react to LH issued boarding passes on AI from DEL-CCU when we do the walk from DEL T3 arrivals to domestic checkin/security

I will keep a printout as back up (as usual).