Until then, we don't really know as viewers exactly where Brian's head is at. ... It wasn't until that song started to play that we were truly able to understand that Brian was, in fact, still trapped in something he was NOT choosing and did NOT control
This scene and song bring up a strange mix of feelings for me - profound sadness at Brian and Justin's loneliness for each other - and at Brian's relative isolation from everyone - and also hope for Brian and Justin's future together; the love is so obvious that we just know they must come together again.
Yet I'd never gone beyond that to consider what we're actually shown about Brian's thinking and feelings. And now that you point it out - yes!! I have to go back and watch 507 again. I've been thinking about it all day, so it must be time.