Yes, because it's his public timeline. But you will not see @replies from people you are not following in your timeline.
Um, thanks, I'll check that! Still, I think it's unintuitive. There's no way I could figure this out from twitter's UI, if only somehow by accident.
I see a lot of Shaun's tweets starting with @someuser, e.g. http://twitter.com/#!/shauninman/status/59266889741905920 http://twitter.com/#!/shauninman/status/59254473125666816 http://twitter.com/#!/shauninman/status/59237467353657344 http://twitter.com/#!/shauninman/status/58999188649807872 and I don't follow him or any of these guys