It's not ambiguous at all. Bruce lives, retires to Europe with Selina, and arranges for Alfred to see him at that outdoor cafe Alfred was talking about earlier.
Hence, the scenes indicating that the autopilot actually worked, that the Bat-Signal was mysteriously repaired, that the pearl necklace was missing . . . all of which are set-up for the Big Reveal that Bruce and Selina are living happily ever after. None of those scenes make any sense or have any purpose otherwise.
Nothing in the script indicated that these things were anything less than concrete reality. All of that happened, just like it says in the script (and, ahem, the book).