Sure as long as the GPU's are using 6-pin PCIe connectors. Many cards are using 8-pin connectors. Beyond that, as long as total power they need is a bit less than the 1600w the Bitmain PSU can supply (ALWAYS give some reserve margin!) yer golden.
He still need a multi GPU setup, since a PC require 4/8 pins for the CPU and 24ATX connector, then the risers need sata/molex, etc. Thus he need to power the risers with the PC's ATX, only then can he use the server PSU to power the GPU's. And he need to power the PSU probably at the same time.