Webmap basemap opacity not honoured

[SamLarsen]

I am consuming a webmap which has an opacity setting for the Bing imagery basemap.  The opacity value is being passed from ArcGIS Online in the webmap JSON but the arcgis utils library is not honouring this opacity value.

esri.arcgis.utils.createMap

The webmap JSON in question is this:

    "baseMap": {         "baseMapLayers": [{             "id": "BingMapsAerial",             "opacity": 0.8200000000000001,             "visibility": true,             "type": "BingMapsAerial"         }],         "title": "Bing Maps Aerial"     },     "widgets": {         "editor": {}     },     "version": "1.6"

I am using version 3.0 of the JavaScript API.

I have reproduced this issue in the following sample:
http://help.arcgis.com/en/webapi/javascript/arcgis/help/jssamples_start.htm#jssamples/ags_createwebm...
Using the following webmap:
http://www.arcgis.com/home/webmap/viewer.html?webmap=b106b3fa92f041668f967b1223cffbeb

Is this a known limitation? Or is this the remnants of the following bug that has not been fixed?
http://forums.arcgis.com/threads/35759-How-to-set-BaseMapLayer-opacity?highlight=bing+opacity

[SamLarsen]

A bug has now been raised for this:

NIM083988 "Javascript application which consumes an ArcGIS.com Web Map, does not honor transparency when using a basemap with Bing imagery."