Regarding Burlington Northern, I've run across two reports in the past. The first is by the Texas Hedge Report and is entitled "Railroads: Following Buffett's Latest Move". This second one was posted on a message board: (hat tip ValueInvestorHaven)
Bottom line is the company has 29000 miles of track which costs about 3 million dollars per mile to "replace" . which totals about 87 billionI can not attest to the validity of that analysis, but if that is accurate that would be an interesting place to start researching. Buffett also mentioned that as fuel costs rise, the comparative advantage of rail vs. trucking widens because fuel makes up less of rail's total costs.
Land which is on the book at 1.7 billion dollars has a "conservative"average cost basis of about 50 years ( some of the purcahses are on books pre1900) at a 3% annual appreciation the land is probably worth more than 8 billion and chances are that number is UNDERSTATED.
The terminals probably are worth another 3 billion conservatively and the long term debt which includes leases is about 11 billion .So 100 billion dollars of assets -11 billion of debt is about 89 billion dollars.The whole company can be purchased for under 28 billion at todays closing price.
I've been looking into USG recently, and I will post some information on that shortly.