I've always thought given the time, Brian would have come around to the fact that he had to figure out a way to get Justin back in his life. I think that by this point he has grown enough to know that Justin makes him happy. But he is too busy distracting himself to notice.
With that in mind, I thought it was possible he could go to Babylon to get Justin back that night on sort of a whim... he hasn't really thought the whole thing through... but he wants Justin.
As for what happens to everyone else, my thought is that everything is exactly the same except for where Brian is and where Justin is that night. Justin is even further away from the bomb because he is on his way to Brian's office. And Brian is close to the bomb because he is at the bar which is where Michael is in canon. Michael's injuries and recovery are the same as canon.
I would like to extend this a bit which is why I haven't gotten around to reposting in my own journal yet... one of these days. LOL!