If I follow this correctly, DAL did two related trades:
Bertans + #10 to OKC for #12 (Basically trading down a couple of spots to dump some salary and I guess create the TPE).
Absorb Richaun Holmes and pick #24
So the net deal for Dallas is:
Out: Bertans, #10
In: Richaun Holmes, #12, #25
That is actually a pretty good net deal for DAL.
I don't think there is anyway that BOS could have done something with them for Grant and #25. There would be no reason to. Grant isn't salary we are looking to dump like SAC with Holmes. That is a really expensive salary dump for SAC, giving up pick #25. Wow.