[Nexus 7 Original Development] mattbirks:
I do have a notification sound set, and that does work.

Here's the logcat for when it plays the default notification sound when I change the Notification volume in settings...

E/AudioTrack( 150): AudioTrack::set : Exit
D/NuPlayerDriver( 150): start(0x4123dc20)
I/NuPlayerDecoder( 150): [OMX.google.vorbis.decoder] resubmitting CSD
I/NuPlayerDecoder( 150): [OMX.google.vorbis.decoder] resubmitting CSD
W/SoftVorbis( 150): vorbis_dsp_synthesis returned -135
W/SoftVorbis( 150): vorbis_dsp_synthesis returned -135
I/NuPlayer( 150): audio discontinuity (formatChange=0, time=1)
I/NuPlayerDecoder( 150): [OMX.google.vorbis.decoder] resubmitting CSD
W/SoftVorbis( 150): vorbis_dsp_synthesis returned -135
I/NuPlayerDecoder( 150): [OMX.google.vorbis.decoder] resubmitting CSD
W/SoftVorbis( 150): vorbis_dsp_synthesis returned -135
I/AudioFlinger( 150): BUFFER TIMEOUT: remove(4100) from active list on thread 0
x40cea008
D/NuPlayerDriver( 150): reset(0x4123dc20)
D/NuPlayerDriver( 150): notifyResetComplete(0x4123dc20)
D/NuPlayerDriver( 150): reset(0x4123dc20)

Here's a logcat for when entering the Other Sounds submenu and disable/enabling Screen Locking sounds...

I/ActivityManager( 551): Displayed com.android.settings/.SubSettings: +409ms
I/Timeline(26766): Timeline: Activity_idle id: android.os.BinderProxy@cae3440 ti
me:23398881
I/Timeline( 551): Timeline: Activity_windows_visible id: ActivityRecord{182ff13
2 u0 com.android.settings/.SubSettings t868} time:23399185
D/NuPlayerDriver( 150): reset(0x41239838)
D/NuPlayerDriver( 150): notifyResetComplete(0x41239838)
D/NuPlayerDriver( 150): reset(0x41239838)
D/NuPlayerDriver( 150): reset(0x416cf378)
D/NuPlayerDriver( 150): notifyResetComplete(0x416cf378)
D/NuPlayerDriver( 150): reset(0x416cf378)
W/AudioTrack( 551): AUDIO_OUTPUT_FLAG_FAST denied by client
E/AudioTrack( 551): AudioTrack::set : Exit
W/AudioTrack( 551): AUDIO_OUTPUT_FLAG_FAST denied by client
E/AudioTrack( 551): AudioTrack::set : Exit

For info, this is when I drop back out of that submenu as the volume change sounds no longer work, as I've mentioned previously....

W/AudioTrack( 551): AUDIO_OUTPUT_FLAG_FAST denied by client
E/AudioTrack( 551): AudioTrack::set : Exit
I/Timeline(26766): Timeline: Activity_idle id: android.os.BinderProxy@3bca261a t
ime:23509227
I/Timeline( 551): Timeline: Activity_windows_visible id: ActivityRecord{33c9421
6 u0 com.android.settings/.SubSettings t868} time:23509464
I/art (26766): Explicit concurrent mark sweep GC freed 9668(793KB) AllocSpac
e objects, 1(16KB) LOS objects, 40% free, 8MB/13MB, paused 974us total 65.718ms
W/MediaPlayer-JNI(26766): MediaPlayer finalized without being released
D/NuPlayerDriver( 150): reset(0x40dcda50)
D/NuPlayerDriver( 150): notifyResetComplete(0x40dcda50)
W/MediaPlayer-JNI(26766): MediaPlayer finalized without being released
D/NuPlayerDriver( 150): reset(0x40d406a0)
D/NuPlayerDriver( 150): notifyResetComplete(0x40d406a0)
I/art (26766): Explicit concurrent mark sweep GC freed 14098(1096KB) AllocSp
ace objects, 0(0B) LOS objects, 39% free, 6MB/11MB, paused 839us total 38.786ms
I/art (26766): Explicit concurrent mark sweep GC freed 3(96B) AllocSpace obj
ects, 0(0B) LOS objects, 39% free, 6MB/11MB, paused 782us total 34.881ms