I doubt that the CC is thinking about taking AZT to trial. Renraku is currently an ally, they've got great public approval, and they took out Bad Dragon #1. Everyone who died under the influence of Blue-227 was an acceptable loss in a war against a terrorist.
if they released B-227 over a neutral city like Denver? oh heck yea they would. Over the middle of the rain forest/war zone? Not worth their effort.
Sadly it's the location, no the act that would get the CC involved. In the middle of the rainforest, there is no real corp interest. Denver City? Filled with consumers, Nations, and Corp citizens that would ALL be affected by B-227? they would be all over it so as to not appear weak. A lot of the CC's power come from their perceived ability to control and contain Mega Corp violence. If they let Aztech get away with using a biological weapon on a populated neutral city, that power base and authority would start to crack as people of the world see them as ineffectual. And if they are ineffectual, why listen to them?
the key here is WHERE is the weapon being used.... in a warzone away from major population centers, no one cares. The spin doctors go to work about the tragic collateral damage, sob, sob, sob.
Which is a far cry different then going after Ghostwalker in a Neutral city housing 4 countries and offices for all 10 MegaCorps and hundreds(?) of AA rated and smaller corps. you have to remember B-227 is not a point and click weapon, it is a mist... which means it is vunerable to air currents..... they Explode it over Aztlan territory, it drifts on the wind and blankets everything downwind of the detonation point.... so countless people would be infected from other sectors/Nations/Corps... and that is when the field day happens.