As the original question asks, yes, you will be able to connect from any Delta branded, or Skyteam flight, and get mileage or whatever.
My question is this: When would you really need to connect from Song to mainline Delta? I mean, Song will not be flying to any of Delta's major hubs, right? So, in theory, the only place you would be able to connect to from a Song destination city, would be to a Delta hub, which they probably fly nonstop to from the city you started in. In that regard, I see connecting through from a Song flight to a Delta flight to be a relatively rare thing. I am sure it will happen, just probably not that often.
A woman drove me to drink and I didn't have the decency to thank her. - W.C. Fields