Simao,
I wonder, would make sense to think of defining a new entity e.g. a "multimedia alert gateway", where we would state what the conversion requirements would be and then we go on to say how it would be handled within H.323? This maybe as an add on to H.323, or perhaps as something that could be used for H.32x (now putting Q1 in the discussion :-) ) and H.248 as well?
My thinking was that the emergency broadcast center was the "gateway", so to speak. I have envisaged that there would be devices that knew where to send H.460.21 broadcasts, as well as devices that knew how to place serial and parallel calls. So, I did expect such an gateway, but do we need a new standardized signaling element for this? It seems like these devices would still be standard H.323 entities, but performing a more specific task. Most of the intelligence relating to when to use what method would be outside of H.323. Paul