grugind,
i'm not sure about ata186, but our cisco guy says it supports t.38 standard for fax-over-ip. avaya supports it from cm2.1.1 version, so theoretically you can use ata186 as a remote ip-to-analog gateway. i'm not sure whether avaya's favourite multitech ip-to-analog gateway supports t.38, but minding its cost it probably would be cheaper and easier use ata186. by the way, it's a very interesting question and i think i should try to resolve it in my lab. if the matter is not pressing too hard, you can wait for the results.