Years ago I use to work in a community peace project kinda place. Some of the volunteers were vegan and we use to make Soya milk, (it was expensive and hard to find)
We used a similar method to the one given on this link. http://ourworld.compuserve.com/homepages/pagro sse/RecipeSoyaMilkTofu.htm
Now it is a lot less expensive and so this is too time consuming and akward. I suppose on a grand scale in a commercial operation it becomes more viable!