A 'hall' is a mounty term used for any fortified or semi-fortified location, often built into the moutainside. Halls could be of any size, and many towns are in fact halls, because they are located within fortified areas.
Nobility, even of non-royal nature may own halls, but there aren't many people in Mounty lands who actually own land.
The way it seems to work is this way. Each family would make known their own requirements for living and for work purposes. In exchange for being allowed to use this land, they would return a portion of what they earn off what they are given. The nobles running a particular hall would have land magistrates (perhaps family members) whose job it is to handle the allotment process for land. The land magistrates would probably attempt to keep things running as smooth as possible, and thus would tend not to change the status quo more than is necessary.
Land in the sense used above isn't necessarily land in a normal sense, but includes privilege to use any space within the hall, such as apartments and small buildings.
The result is that families wouldn't have to worry too much about being uprooted, so long as they keep track of their 'taxes' so to speak. In all practicality, the setup for which land they could use would be stable enough that it would be no different than if they did in fact own it.
The 'taxes' tend to be based on goods and services, rather than currency. So a farmer would turn in a portion of his crops, a hunter a portion of his kills, an animal farmer a portion of their animals, and a person in the service industry would make his services available to the government.
The Mounty system seems to be a monarchy with a manorialistic economy.