Until I know how those are shown in chat/irc or how to get them from API there wont be any support for them, for now.
Traditional new subs are a twitchnotify message, there is nothing in the new documentation and I cant find anything about it.
Also I think you need to have Prime subscription notifications enabled in your channel for it to show in your chat when you use your free sub.
If anyone wants to help figuring it out, send me private message with your email I can send you custom version with irc log enabled you can help find out what is shown in irc once prime sub is added.
[Edit] Never mind I fixed it, it is still shown as twitchnotify message and it looks like this "kympy just subscribed with Twitch Prime!"
Should work now, redownload FSN