Not sure if this has already been mentioned here, but since I did a bit of work to figure this out, I figured I'd share with the net.

Nero Digital Audio Reference MPEG-4 & 3GPP Audio Encoder
version 1.0.0.2 (build May 26 2006)

Tested quality-based encoding in steps of 0.025 to find which profile the encoder automatically selects.

Quality 1.000 through 0.325:
MPEG-4 LC-AAC

Quality 0.300 through 0.175:
MPEG-4 HE-AAC SBR

Quality 0.150 through 0.000:
MPEG-4 HE-AAC SBR PS

Of course, you can override which profile you want to use with the -lc, -he, and -hev2 switches, but I just wanted to know where the transition points were in the automatic selection.

Hope this helps somebody!

I think I actually already posted this?

You did.