-=::) Dante (::=-
1. When a player has completed a major line, does this immediately get reflected on the income track?
Yes. The only points that are scored at the end of the game are the Baron Cards.
From the Railways of the Eastern US Rule Sheet:
once a major line has been completed by a single player, that player receives the points on the card and the major line cannot be scored by anyone else.
I assumed that you would put a control locomotive on an incomplete track that you are in the process of laying