Distinguishing multihoming from traffic engg.

Hi, How does one find out if a prefix is due to multihoming or traffic engineering if the Origin AS is different from that of the parent prefix and there is no Origin AS path-prepending? (apart from looking up whois) Even if there is Origin AS path-prepending how do we know that the prefix is due to traffic engineering and not due to multihoming? Roughly what percentage of prefixes which are holes that have an Origin AS different from that of the parent would be due to due to multihoming? Harsha.