It does. Any system that can support 2.8GHz Xeons is almost guaranteed to support 48-bit LBA.
In your case, it uses Intel's 860 chipset, which has 48-bit LBA compatible UltraATA/100 support. (Technically, it is that it includes Intel's 82801BA 'ICH2' I/O controller hub, which, according to Intel's website, supports 48-bit LBA. Any Intel 8xx series chipset supports 48-bit LBA.) But, SuperMicro had to include 48-bit LBA support in the BIOS. Which they almost guaranteed have done.
Also, if you are running Linux, BSD, Solaris, Windows 2000, or Windows XP, it doesn't matter if the BIOS has 48-bit LBA support, the OS ignores the BIOS and provides native 48-bit LBA support with your chipset.
Thanks so much for the info!