To my knowledge, the reason the Northerns, Berkshires, Daylight were removed from the Gtrax store is that demand "has dwindled to less than a trickle" and they need reformatting for 2013 anyway, so they'll hopefully be back on Steam soon, so says the updates from Gtrax.
Reformatting's supposedly why the Challenger and Big Boy were pulled too...Thank God I bought the former when I did.
I'd've really loved to buy the Berks and maybe the Daylight direct from Gtrax, the coach packs too, but it looks like that's just a pipe dream now..Darn it...