in my testing at bing.com/maps i've never been able to identify more than 20 levels of detail, and only in specific areas where data is available (for example at the corner of E79th St and 5th Ave in NYC).in order to push this additional level of detail to a Bing layer in the Esri JS API, you have to do something like this...
dojo.connect(veTileLayer, "onLoad", function() {
console.log("ve: ", veTileLayer);
veTileLayer.tileInfo.lods.push(new esri.layers.LOD({
level":20,"resolution":0.149291071,"scale":564.248588,"startTileRow":0,
"startTileCol":0,"endTileRow":1048575,"endTileCol":1048575
}));
veTileLayer.scales.push(564.248588);
map.addLayer(veTileLayer);
});
}