This is the best I've been able to do.
bec-submarine is a flat yellow FFE757 dds -- no alpha.
This is reflectcube2.dds -- a new texture. This needs reworked a lot, but the trick at the moment seems to be to take some of the underlying bec_submarine colour and some of the nightlight colour so at least it looks like it might go with either type of ambient light. It's a real fudge, but until the night light controller is exposed I'm at a loss as to what else to do.
It is saved as a DTX1 cubemap <---important
Then the sim file has been edited in goblin.
In this case merge (data/submarine/common/rooms/...) Room_DER.gr2 and Room_DER.sim
Once it's open click on GLASSDOMES in the scene tree and edit the behaviours. In the example here EnvMappingCtrl has been edited:
Type: changed to 'Cube' (originally Sphere)
Teture Path: data\Textures\TNormal\tex\ReflectCube2.dds (was ReflectCube.dds)
Reflection Multiplier: 3 (was 9.9)
Fresnel Factor: 0 (was 0)
This is all affected to some degree by the HDR_interior_submarine.cfg