from the Points Transfer Rules 101 thread:
"d. Transfers are only processed immediately if you are working with your Current Use Year, and the transferrer and recipient are in the same Year of their Use Year. (For Ex. if done today, a transfer from Dec03 UY to Jun03 UY is immediate, but from Dec03 UY to Apr04 UY needs to be done manually.) This is the only time that an automated Transfer Confirmation Number is generated. All other Transfers have to be done manually, and can take up to a few days to be completed."
(keep in mind the above info was given to me by only one MS CM, so it's possible there are other circumstances where transfers are processed right away.)
from my own personal experience, a manual transfer can be done as fast as the same day, or as slow as 3 days later.
HTH!