How to set Vertical Coordinate system when creating a 3D shapefile?

Question

I'm working with GDAL v1.11 and am seeing the vertical CS stripped when exporting a 3D shapefile (from oracle spatial). This is the command I'm running:

ogr2ogr -f "ESRI Shapefile" B_POINT.shp (oci_url) -sql(sql_select_statement) -nlt POINT25D -a_srs "EPSG:4326+3855" -nln B_POINT

I've tried specifying the a_srs with several different options

EPSG Code: "EPSG:4326+3855"

PROJ.4 Definition: "+proj=longlat +datum=WGS84 +geoidgrids=egm08_25.gtx +vunits=m +no_defs"

Filename: /apps/gdal-1.11.0/compound_wkt.wkt

Where file>cat /apps/gdal-1.11.0/compound_wkt.wkt

COMPD_CS["WGS 84 + EGM2008 geoid height",
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0,
        AUTHORITY["EPSG","8901"]],
    UNIT["degree",0.0174532925199433,
        AUTHORITY["EPSG","9122"]],
    AUTHORITY["EPSG","4326"]],
VERT_CS["EGM2008 geoid height",
    VERT_DATUM["EGM2008 geoid",2005,
        AUTHORITY["EPSG","1027"],
        EXTENSION["PROJ4_GRIDS","egm08_25.gtx"]],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AXIS["Up",UP],
    AUTHORITY["EPSG","3855"]]]

I haven't had any luck in exporting the vertical CS with any of these ogr2ogr a_srs options. I've even installed PROJ.4 and tried setting the s_srs and t_srs with no luck.

The egm08_25.gtx file is downloaded and copied to /apps/proj-4.8.0/nad/ directory, per this post: http://osgeo-org.1560.x6.nabble.com/GTX-format-td3840948.html

Is there any way to export the vertical CS for a 3D shapefile, or is this still a bug? I have the same issue trying to export a FileGDB.

EDIT: I can view the WKT of the compound CS here:

gdal-1.11.0>testepsg epsg:4326+3855
Validate Succeeds.
WKT[epsg:4326+3855] =
COMPD_CS["WGS 84 + EGM2008 geoid height",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4326"]],
    VERT_CS["EGM2008 geoid height",
        VERT_DATUM["EGM2008 geoid",2005,
            AUTHORITY["EPSG","1027"],
            EXTENSION["PROJ4_GRIDS","egm08_25.gtx"]],
        UNIT["metre",1,
            AUTHORITY["EPSG","9001"]],
        AXIS["Up",UP],
        AUTHORITY["EPSG","3855"]]]

Simplified WKT[epsg:4326+3855] =
COMPD_CS["WGS 84 + EGM2008 geoid height",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433]],
    VERT_CS["EGM2008 geoid height",
        VERT_DATUM["EGM2008 geoid",2005],
        UNIT["metre",1]]]

Old Style WKT[epsg:4326+3855] = GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433]]
ESRI'ified WKT[epsg:4326+3855] = 
GEOGCS["GCS_WGS_1984",
    DATUM["D_WGS_1984",
        SPHEROID["WGS_1984",6378137,298.257223563]],
    PRIMEM["Greenwich",0],
    UNIT["Degree",0.017453292519943295]]
PROJ.4 rendering of [epsg:4326+3855] = +proj=longlat +datum=WGS84 +geoidgrids=egm08_25.gtx +vunits=m +no_defs 

The "ESRI'ified WKT" is what I see in my exported shapefile and filegeodb:

shapefile>ogrinfo -al B_POINT.shp | more
INFO: Open of `B_POINT.shp'
      using driver `ESRI Shapefile' successful.

Layer name: B_POINT
Geometry: 3D Point
Feature Count: 1
Extent: (39.212616, -6.130917) - (39.212616, -6.130917)
Layer SRS WKT:
GEOGCS["GCS_WGS_1984",
    DATUM["WGS_1984",
        SPHEROID["WGS_84",6378137,298.257223563]],
    PRIMEM["Greenwich",0],
    UNIT["Degree",0.017453292519943295]]

I know that shapefiles support vertical coordinate systems (e.g., page 26 here: http://www.geo.hunter.cuny.edu/gis/docs/Whats_New_In_ArcGIS_92.pdf). There must be a configuration in GDAL to get the shapefile ESRI WKT to pickup the compound CS.