Ha ha I can reply with information to my own request as I traveled up there by the said train. It departs on Monday and Thursay from Choibalsan to Chulunnkhoroot at 4pm, there are two carriages for passengers, the rest are for fuel and cargo. There is only hard seat and the cost is 4500 Togrog. Its slow, can take an agonising 8 hours to cover 200km but its an interesting journey and the Mongolians liven it up. There isn't really any place to stay in Chuluunkhoroot though the National Parks office in Choibalsan have contacts who can help. The word is that a permit is required to go up here as its 3km from the Russian border and the army have a 30km zone South from here that they patrol. However I never took one as its only available from Ulaan Baatar and I never got stopped. The poice didn't seem interested but doesn't mean to say they couls be trouble. The Daguur B is an interesting area, plenty of Gazelle and wildlife here.