According to the servlet 2.4 spec, the run-as should be used for Servlet.init()
page 285:
" Clarification: run-as identity must apply to all calls from a servlet including init() and destroy() (12.7)"

This isn't working.

Rather than breaking all the web integration tests with a deploy time error to prove the point, I'm attaching an example.zip

% unzip example.zip
% cd example
% edit build.properties to point at JBoss
% ant deploy

The web integration tests do need updating to test for this.