My system is there is a function, call it sin(Y) (but it can be any periodic function), that generates deposits. Sin(Y) has range -1 to 1, so if you drop randomly, there is 100% chance you'll hit a value from -1 to 1 or [-1,1], a 50% change you'll hit a value from [0,1], a 25% chance of hitting a value from [0.5,1]. etc etc.
All MA has to do is control the loot window, the number A for [A, 1], to control returns. When the window is very wide, such as [0,1], then for a person dropping randomly, there is a 50% chance of hitting on the first drop, 50% of hitting on the second drop, etc etc... so there is a 25% chance of hitting 2 consequentive deposits, i.e. a 2 claim vein, a 12.5% chance of hitting a 3 claim vein, a 6.25% chance of hitting a 4 claim vein, etc, so veins appear by chance.
There is also a more direct way, and that is to make the window the widest possible, i.e. [-1, 1]. Then every drop will hit 100% of the time, then you're guaranteed to find veins, for as long as MA keeps the window so wide. I am fairly sure that this does occur and quite frequently, so everyone has found veins at some point. It doesn't hurt MA to give out 100% hits for a minute because they have total control and can close the window up after a while to suck peds away.