In real world terms Buffy was unable to be wih Angel because of the networks, but if we suspend belief for a moment and that was the real world, if Angel had known Buffy was in Heaven, do you really see it possible the events happened as they did.
It just doesn't work.
Even if they had been on the same networks he still would have been going back to L.A. and she was still going back to Hell, as she saw it, so yeah I do think it still would have played out the same way, unless we go completely mental and make it that Buffy goes to L.A. or Angel comes back to Sunnydale.