I would've posted this directly on SC4Devotion (don't have an account), but maybe somebody could redirect them here.
I was looking forward to project Symphony and you can imagine my frustration when I noticed it didn't work (yes, I did check Maxis Highway Override).
After removing old NAM, reinstalling new NAM, removing game, reinstalling game with only new NAM, it still did not work.
Then I tried to look at the install log, which scrolls by pretty fast. Here is what I found:
The NAM setup must be run with Higher Priviliges, an Administrator account (my User account isn't an Administrator account).
You get to choose the install location when you choose the Custom Installation type.
As standard location, you get presented with the Documents folder of the Administrator account.
Evidently you input your own Documents directory.
Then you choose your install options: check Maxis Highway Override
Install, start game ... no project Symphony.
This is what happened: the setup installed the files necessary for project symphony to function (including some other stuff) in the Documents\Simcity 4\Plugins folder of the Administrator account.
If you copy the folder z___NAM to your own Documents\Simcity 4\Plugins folder, BAM, project symphony works.
Hope this helps some people as I've seen some people having troubles.