If this guy has a snatched copy of the beta's from Apple it is very possible. See Apple has been testing the x86 archetecture for nearly five years now, thus their drivers back then would be for the latest hardware or suspected hardware. Ie. PCI Express which was not yet mainstream and which Apple currently uses would have been the testing bed for their beta program. They would have looked for the most advanced Intel chip and chipset to beta test. Now the P4 is fast, but it would not have been the testing platform. No, Apple would have looked at the PM and Centrino to test. Now we know the drivers would have been configured for these parts, we also know that even if they chose the P4 to beta test, they would have still used the pci express.
The only problem is to wonder whether they would have left the drivers in the kernel as they created Tiger? They must have had the heads up at least three years ago regarding the dual core processors, and IBM certainly would have let them know about the cell processors. We also know that Tiger has been in developement for 1-2 years, so the betas that were produced with that early version of Tiger are probably not very reliable.
I come from the land of Linux, so we are very interested in this development. One reason is that there is a possiblility that hackers could take the x86 drivers from 2.6 kernel and use them if in the minimum as a guide to backwards engineer the necessary BSD/Unix drivers.
For those doubters, you should know in advance that although this may be a permature beta, or even a hoax, that doesn't mean it won't be on the horizon. It will not take long at all before the code engineers figure out a way to break the encryption and develope basic drivers so that it will install on i386 machines. It is just a matter of time. Some of suspect that is exactly what Apple hopes for. It will be the perfect advertising. Tease people with the potential of have this great OS and then convince them that to run it properly you should just fork out the cash and buy a machine.