I've been involved with three stuck seatposts on low-to-medium end Bianchis over the past few years. All of them had the same problem: really thick tubing reamed down to 27.0 or 27.2 to a depth of six inches or so, with a shallow step back up to the uncut diameter. In each case, somebody apparently forced the seatpost into that step, with the result being a truly stuck post. Heat, penetrating agents, and really big vises don't work - I actually managed to unbraze the seatstay caps/plugs from the seatstays on one frame, while using the frame itself to torque the post in a vise. In each case, I had to cut the posts out with the old hacksaw-in-a-handle trick.