The page turning animations in an exported swf are accomplished via ActionScript—they are not timeline based tween animations. You might be able to decompile the swf and get to the code, but I've never tried it. Google SWF decompiler.
When you export to fla the animation ActionScript code is not included, so you lose the page turn animations. Each spread is saved as a MovieClip and the clips appear on sequential keyframes of the root timeline. With an fla it's up to you to write any animation code.