For devs watching this and think they can help.
Audio RIL is completely broken. Samsung is using some magic sauce in their stock roms to get ril audio path to connect. I couldn't figure it out with CM10, that's why we're still using HAL there.
Here is what I do know: Samsung does not use libsecril-client.so in the LTE variants of the Note 2. Remove the file from stock or cm10, and the thing will work just fine. It does do the routing through another file that audio.primary.smdk connects to: libaudio-ril.so. I have no source for this one, it's all just one big black box at this point. libaudio-ril.so is different from libecril-client, it doesn't share the same symbols. libaudio-ril.so requires several other files that they, in turn require the same shared libs that the ril library shares:
libcsd-client, libssaudio-client and libtinyalsa.so to name a few.
We can't move the HAL stuff to this rom because 4.2 is using different APIs and audio.primary.smdk* (from HAL) won't load because it can't link some functions at load time. It'll complain about undefined symbols.
We can look at some of qualcomm's routing implementation given that they're open source and readily available "audio.primary.msm*" that the d2 variants rely on, or ... I don't know. I'm out of ideas at the moment.
I'm done for today. Adios.