there hasn't been any concerted effort to support WAP
That said, JBP 2.2 has a very clean separation of concerns. The content type, encoding, etc. is isolated into a StreamInfo class that gets instantiated in the server invocation and is available downstream. What I'm not clear about is if you want a mixed portal (support for WAP and HTML, ...) how do you determine what page to serve ? There is currently no facility that would allow you to map a default page per content type.
The portal would have to choose the layout jsp based on the content type, or other cc/pp header information.
There is a URL mapping facility, but it isn't geared towards this use case.
The short answer: I'm not aware of any WAP examples