I've been looking at this, after finding some aircraft that show a shiny / chrome finish in FSX but are dull in P3d
I've knocked up a model with 4 spheres, all with basically the same material settings with a couple of differences.
Here's how it looks in FSX & P3dv2.4:

and in P3d V2.5(hotfix)

Sphere 1 has "use global environment map as reflection" ticked, and "GlobalEnv_AC_Chrome" set as the reflection map
Sphere 2 has "use global environment map as reflection" ticked, and nothing set as the reflection map
Sphere 3 has "use global environment map as reflection" unticked, and "GlobalEnv_AC_Chrome" set as the reflection map
Sphere 4 has "use global environment map as reflection" unticked, and nothing set as the reflection map
It seems using the "use global environment map as reflection" setting in the material properties isn't working, and is killing the reflection.
Hope this can be fixed in the next patch.