Maybe I should expand a little.

If you are accommodated on a carrier other than your original one, then you can get mileage from the other carrier and the original one.

I was flying GRU-IAD-SFO in C on UA - but the UA flight cancelled so I was put on RG from GRU-MIA, and then connecting onwards on AA and UA. I received LH miles from RG, and UA miles from my original routing to IAD.