It's the ticketing carrier and fare class that counts, not whose airplane you are traveling on - the exception being CO/COEX flights booked on co.com. If you ticketed on co.com with a CO ticket, and flew CO metal, 100%EQM is assured. Likewise, if you booked anywhere else for an AS ticket in any fare class, you would earn 100%EQM. Almost all published AS fare classes earn 100%EQM.

Any DL ticket booked in their L,U,T class regardless of the booking mechanism is 50%EQM, likewise any NW ticket in their V,L,T,K class is 50%EQM regardless of the booking mechanism - and in both cases, regardless of who is operating the flight. Any CO ticket in the deep discount bucket operated by NW or DL is also 50%EQM.

In short - either ticket your itinerary on AS stock with an AS fare code, or you will earn 50%EQM in the example you cited in the post.