Yeah i was wondering about that snowy lookin place too.. I just now got to EOS so i couldn't answer you're question as to weather you unlock it or not, but i always just assumed you would..
As for finding the rail gun i'am not even sure who i picked mine up off of.. I think it was some mission where u had to eliminate some snipers or something.. But after playing the singleplayer all day usein it i'am beast now on multiplayer with it.. I'am almost guarantee'd 2-3 kills with it everytime i pick it up.. Especially on Siege on the level overpass i just stay under the bridge and pick off the people goin to attack/repair it.. Man, overpass is a dope ass map all around for snipeing/rail gunning..
Fuck.. I jus got off work.. Worked 2-10.. I jus got done smokein a bowl.. Bout to pass out.. Wake up around 5-6, get some more buds, try out that angus burger at mcdonalds, come back home and get down on some Siege for a few hours.. Haha i got today off, and all i plan on doin is sittin in my bed sleepin and playin video games, yee!!
get on later tonight pbarb.. you can join me and a few of my friends playin Siege... We always win.