AI have checked by bags successfully in Delhi, many times, through to DCA in Delhi on two separate tickets. One was DEL-BKK on AI and he other was BKK-NRT-LAX-MSP/DTW-DCA on NW. NW and AI do not code-share. A code-sharing agreement between the two airlines is not necessary requirement. All that is needed is an interline ticketing and baggage agreement. However, the person checking you in DXB has the immediate say. Tings could go wrong on BOM too.