Answer
The only Eos family consoles that support a splitter for a video port are the ones that used an Intel or Radisys motherboard (the first itration of Ion, RVIs, and RPUs). The video card for these consoles has a single dual-DVI-I port and was specially designed to send two signals out that port through a special splitter cable (ETC PN M7186-F).
All other ports on any Eos family console only send one signal and support one monitor display. If you use a splitter and plug more than one monitor into that splitter, each monitor will display the exact same data.
Reference images for the dual-DVI ports:
RVI:
Ion: