Not unless he hacks the drivers for the mobo which will be a pain in the A$$.
SLI and Crossfire mobos work like this:
->ATi crossfire and Intel dual PCI-E boards only support only dual ATi cards. (AFAIK, Intel hasn't released an SLI board)
->NVidia SLI boards only support dual NV cards.
He can, however, use a single GTX on the ATi board.