MT law says you cant CONCEAL in a room or area of a building that's purpose it to sale, dispense AND consume alcholic beverages. That being said any restaraunt that has a bar seperated from the dining room (most do seperate them) it is legal to conceal with license in the dining area because the drinks are dipensed in a different "room".
No law in MT prohibits Open carry of firearms but allows bussinesses to ask you to leave. I am planing a trip to MT this summer and been studing up on them. If your afraid somone one might ask you to leave Chille's or Outback type restaraunts just conceal and make sure its not a sloppy conceal and you should have no issues. I have also heard that Missoula has banned open carry but have not seen the black and white on that.
Ohh yeah and no carring on the trains.