Thin ethernet cable needs tight impedance match and a terminated load to prevent ringing/reflected waves at LAN frequencies of 10mhz and above.
As far as I know WORDCLOCK out is the buffered master device's sample clock. Termination not necessary at those frequencies but I would use a good cable of modest length.
Keep us posted on using the wordclock via the BNC connectors. I'm kind of curious as I have read a glowing review of the 2408 this morning. I may consider it later this year.