If it is to CIC-Buffalo, I can verify that I faxed a letter and a copy of the email from CIO-Sydney, that was sufficient (no hardcopy by regular mail/courier). They replied by email after 2 weeks, confirming withdrawal.
Yes, full refund. Just to be safe, my request was for withdrawal of my application AND a refund of the application fee I presume it should be automatic, but clarity doesn't hurt... You're eligible for the refund even past the 120-day deadline, as long as it doesn't go into "processing stage" (which it shouldn't if you haven't submitted the full application).