If you're doing this and it doesn't work, then you should post your entire cmd line:
---- from the admin guide ----
15. Apply the mst transform file to the expanded MSI in the AIP (note the use of the ``/i`` switch rather than ``/a`` or ``/p``).
msiexec /i <AIP distribution point dir path>\<ProductName>.msi
TRANSFORMS=<AIP distribution point dir path>\<ProductName>.mst