yes, of course.
I thought I read somewhere that once you purchased them on your iPad you couldn't move them but I guess I was wrong then.
Have you actually done this yet?
yes, you can do this.
I bought a book on my iPad, and sync'ed same book to iPhone via iTunes. Bookmarks transfer too.
You don't even have to move them, you can have them on both at the same time.
...and they are synced to the same page (or more preciously same place) every time you exit iBooks.