I've also read two specific German beer history books, and neither one mentioned much about ale brewing in Germany, other than wheat beers, after the early 1500's, probably because of that oh-so-famous tax law...
Germany has a pretty rich tradition of ales, even through the 19th century. Lower Saxony in particular was well known for it's ales, including the now gone
erntebier (harvest beer) and still popular Altbier. Other German ales included, Broyhan Alt, Einbeck, Gose, Lichtenhainer, Grodzisk (still produced in Poland), Malzbier, Süßbier, and forms of
braunbiers or "brown beer."
The only problem I have with calling an Austrian beer from the Napoleonic Wars period a "vienna lager" is that this style wasn't around for another 30 or so years after the war. Also, it wasn't until the mid 1800's that lager brewing began to overtake the native ale brewing in the areas outside of Bavaria. For instance, Bohemia was primarily an ale brewing nation until 1860 or so when you have a dramatic shift to lager-bier. This is important, as we all know that Pilsner was invented in 1842 (it would start to become popular following the World Exposition in Paris, 1867). There were, however, types of lager-ale hybrids brewed during this same period and I concede that Austria was one of the first nations to take up lager brewing outside of Bavaria. Yet, how many took it up lager brewing and exactly when, we don't know.
Aside, we must remember that lager brewing does not make for inexpensive brewing, as you need large support structures for lagering (and ice) and the capital (money) to fund such production. Ale production is much less demanding, meaning more people brewing ales (especially for domestic use) and more ubiquitous.
Here is an interesting piece on Vienna "Ale" Brewing in the 1830's. Ron is pretty much the definitive beer historian around...
http://barclayperkins.blogspot.com/2009/05/brewing-in-vienna-in-1830s.html