I work for a telco, and I know of no feature that will allow you to identify a CO line in the way you are trying to accomplish. We have a "quiet line" that puts a brief tone on the line which is used for measuring loss, noise, etc. on a cable pair, but you have to call on that pair for it to work. Looks like you have to get the telco there to tag, or get out the toner and start sniffing things out.
