The "Jawbone" Montana Railroad between Lombard and Maudlow was for most of its existence part of the Milwaukee Road's Pacific Coast Extension. It would be more commonly called this than "Jawbone" or Montana Railroad (I have never heard it called the Jawbone before). As far as access is concerned, it is physically possible to hike or bike the entire route but it is now owned by numerous individual ranch owners and would take significant time to track down the owners to get permission (I believe Ted Turner owns as least some of this land). I would not recommend accessing without permission as individuals out there may shoot first and definitely do not like trepassers.