I was just about to congratulate you for fixing your steering issue in only 2 hours!
The likelihood of a shop getting it out is 100%.
After all you seemingly did today, I understand you don't want to try, but there are lots of things you could try...but I understand you just want to know it can be done.
At the worst, a shop should be able to weld onto the broken bolt and unscrew it that way. I'm not sure what's on top, but I wonder if you could get it out by just turning it in more. Dremel a slot in it...drill a hole in it and use extractor.
Not sure what tools or access you have...but a shop can do it...assuming you have one with experienced guys around.
Upcoming NYC dates: Jan 8 and 27. See Facebook for other shows and PM me if you can make one...love to see you there!
Mangofy your E46!