I think there's been a misunderstanding. I think he's saying that he's not getting the 360 to work at all through the Y/Cb/Cr input on the TV, it only works on the Y/Pb/Pr
After looking at your manual and noticing that it does NTSC and PAL I would venture to guess that your tv has been designed to accept any type of input you can throw at it including the rarely found Y/Cb/Cr in order to make it internationally friendly.
Y/Cb/Cr is basically the digital version of Y/Pb/Pr
(just because the cable is a 75 ohm RCA cable doesn't mean it has to be analog).They can produce the same resolutions, but one is analog and one is digital. I can't really think of anything that would output Y/Cb/Cr in 3 RCA component video form. Though I'm sure there are things, I doubt they would be of interest to you.
Y/Cb/Cr is usually found only in HDMI, DVI-D, and DVI-I connections. But don't go trying to splice into any of these to tap into the Y/Cb/Cr as the HDCP would probably thwart the attempt.
unfortunately the answer to your question is that that input is more than likely useless