Wow.. been a rough few weeks.. 11.2 was causing some serious issues with the Buffer Events for publishing streams not working.. and I was fighting with why AEC had stopped working.
After MUCH code teardown and debugging.. it turns out that if you set the bufferTime property on the netstream you're playing on to 0.1 then AEC fails. Like so:
ns_other_guy = new NetStream();
ns_other_guy.bufferTime = 0.1;
As soon as you publish your stream and start playing the incoming on.. AEC doesn't work. Setting the value to anything other than 0 causes issues.
I hope this helps save someone some cycles..