On the CSP side you need Reflections FX on with at least "Refracting surfaces for cars" enabled, maybe also interior masking and local cubemaps (I don't think those are meant to be required but when I tried, one of them was necessary). There's also a Shader Extension Debug app that's pretty necessary, ingame it's called "ReflectionsFX debug". The app's kinda quirky and you don't want to open the "direction" tab in the F5 camera cause the controls conflict very heavily.
For the car you add a section for each bit of glass you want it applied to, to the car's extension ini.
Code:
[REFRACTING_HEADLIGHT_4]
SURFACE = Taillight_Other
INSIDE = Taillight_SUB0, Taillight_SUB1, Taillight_Brakeglo
RELATIVE_TO = PARENTS_PARENT
ABSORPTION = 0.006
AMBIENT_MULT = 1
BASE_EMISSIVE_K = 0.04
BOUNCED_BACK_MULT = 0.89
BULB_BLUR_K = 3.1
BULB_REFLECTION_K = -0.1
CUSTOM_BULB_0 = 0.49, 0.49, 0.05, 0
CUSTOM_BULB_1 = 0.55, 0.521, 0, 0
CUSTOM_BULB_2 = 0.5, 0.5, 0, 1
CUSTOM_BULB_3 = 0.5, 0.5, 0, 1
DIFFUSE_MAP_FILTER_MULT = 3.66
DIFFUSE_MAP_MULT = 1
DIRECTION = -2.39438e-05, -1, 1.75032e-05
DYNAMIC_EMISSIVE_MAP = 0
EMISSIVE_MULT = 0.19
EXTRA_SIDE_THICKNESS = 0
F0 = 0.27
GLASS_COLOR = 1, 0, 0.0680938
GLASS_EMISSIVE_MULT = 0.2
GLASS_EXTRA_THICKNESS = 0.0041
INNER_SPECULAR = 10
INNER_SPECULAR_EXP = 795
IOR = 1.6
IOR_FLYOUT_FLAT = 0
LOD_BIAS = 0.3
MIRROR_DIR = 1.00228, 9.76771e-06, 8.48505e-06
MIRROR_POS = 0, 0, 0
NM_SHARE_EXT = 0
NM_SHARE_INT = 1
ORIGIN = 0.60141, 2.07294, 0.799355
RADIUS = 0.1704
RAYTRACE_STEP_INCREASE = 1.11
RAYTRACE_STEP_START = 0.02
REFLECTIVENESS_DIFFUSE_MULT = 7.2
REFLECTIVENESS_MULT = 2.6
REFLECTIVE_GAMMA = 0.2
SIDE_FALLOFF = 1.62
USE_COLORED_BULBS = 0
USE_CUSTOM_BULBS = 0
USE_NORMAL_ALPHA = 0
I believe if you just include the top 3 lines the app will generate default values of the rest for you. SURFACE is the name of the glass with normalmap, INSIDE is a list of every object behind it. From there it's just moving all the sliders until it works right. The ORIGIN and RADIUS should be put so that it covers the whole glass, and DIRECTION is the way you see the light brightest from.
After you tweak stuff in the app click "copy settings to clipboard" and paste the values it gives you (everything from absorption to the end)
I drew the white arrow at the point that actually matters, the yellow thing seems to drift with my AC setup but that xyz thing is where the ORIGIN actually is. As you can see it's fully behind the light object, and pointing inward.
Since I'm building the model while adding this config I have only the lightbulbs light up in the car lights.ini, if you've got something else going on you can check "use custom bulbs" and position the source of the light manually.
In my experience you need a separate bit of glass for each emissive object, otherwise it does something stupid. So I have 3 separate exterior models. The non-emissive interior's just a single object listed under each of them, and the emissive part's separate for each so it can go in lights.ini.