Yes, but both OS X and WinNT are basically portable systems that don't rely much on the firmware/bios to get the job done. OS X has run on PowerPC/x86 for a long time. WinNT ran several other processor architectures before Microsoft lost interest.

No doubt a Macintel machine will have a PCI bus, USB ports, Fireware ports, a SATA controller, the same types of video cards, same type of memory system etc etc as an equivalent Wintel machine. Who knows it may even use a very similar north-south bridge and the like.