I have just release iKatastr2 app on AppStore (free) that  might be useful for you to look at as it uses WMS sources and  custom tile loading on top of google.

App does simple stuff – shows cadastral information by tapping on cadastral  map of the Czech Republic.

As all is driven by JSON configuration it is quite easy to render similar information from other sources.

http://itunes.apple.com/us/app/ikatastr2/id545292674?ls=1&mt=8

enjoy !