Yep, those are the ones....
I wanted to replace them, but couldn't get them out.
I didn't want to apply too much force since I wasn't sure if I could get them out, so I wanted to make sure the thread stayed ok...
In your case, since the bolt is already busted, I would try whacking it with a hammer, just make sure you don't bent the mounting plate. Otherwise I'm affraid you will have to drill them out
Rob.