Depending on where it broke you may be able to get it out with a magnet. Only half of it is threaded, the remainder is a thin pin. If just the pin part is in there, try tapping the cross pin back and forth to loosen it up and see of you can draw it out. Otherwise you will have to drill and try to extract. It's gonna be a PTIA because of how little space there is and how small the bolt is. Those threads are pretty fine and you could damage them if you don't get straight on the bolt.
Patience is key here, forcing it will only damage the carrier. Cross pins are easy to remove and replace, pulling a whole gear set is a little harder.
I think why these break is because the cross pin still has pressure on it from the spider gears and it creates a lot tension on the bolt causing it to snap when you try to remove it. Also, I think Ford may have put a form of Loctite on the threads.
I have only had one break on me, but it was at a junkyard, so no loss there other than not getting to the part I wanted.