Well, I always build/buy my servers with ECC memory, I'd kinda hope Dell would do the same with its rack-mount servers. So I suspect that's the case.
We'll also have to see if it's RDRAM or SDRAM ... remember the i840 and i850 chipsets supported RDRAM directly and that the RDRAM->SDRAM conversion chip was recalled by Intel due to bugs and that chip didn't support ECC, either. So there's a good chance that we're looking at ECC RDRAM ...
But until Ben gets back to us ... who knows?
It might be PC 66 :)