My impression– for a few different reasons –is that it will not work, at least not yet. There are some unresolved issues with Leonardo and ArduinoISP that have been reported in the forums.
Additionally, it may not be possible to use the Leonardo for this because of the pin routing– apparently it’s SPI pins are not fully shield compatible: http://petervanhoyweghen.wordpress.com/2012/09/16/arduinoisp-on-the-leonardo/
