Boundary lubrication happens in the crosshead. Lubricating quills are nothing but pores or holes in the cylinder liner through which lube oil is inserted into the cylinder. Alpha lubricator has a multi-piston ( very small pistons ) assembly that inserts a limited amount of lube oil into each cylinder through quills after each second revolution. Although it is not the same but works somewhat similar to the plunger type fuel pump. Will write in detail in a new post later.