A while ago, I manage to get a stuck seatpost out the frame, it wasnt easy though, it took 3 of us to do it, we place the seatpost on a heavy duty vice with the frame upside down and put some heat on the seatpost tube frame (it's ok if you wish to have the frame resprayed afterwards) after getting it hot, we dipped in cold water and then back on the vice, 3 of us turn the frame round and finally it moved, it took well over 20 turns to get it out.
You need to put heat on it for the metal to expand and then dipped in cold water for the metal to shrink abit, it's depend how stuck it is I guess, good luck on it.