If you have ever had the need to call a package file in either the Initialization Phase or the Before File Extraction Phase, the new feature in PB3: “Loader Temporary Resources” found under the section “Advanced Build Options” is your answer.
As soon as your package executable is run, a temporary folder is created and accessible by the PB variable:
%PBSFXPATH%
Your file(s) are extracted to this folder and accessible for any custom action at ANY time up until the executable closes. Very nice.