"Error page mechanism operates on the original unwrapper/unfiltered request and response objects created by the container. The mechanism described in Section SRV.6.2.5, *** "Filters and RequestDispatcher" may be used to specify filters that are applied before an error page mechanism." ***
SCJP | SCWCD | SCBCD | SCWSD 5 | SCEA (I) 1.4 | SCEA 5 | IBM SOA 669
I think this is related to <dispatcher>ERROR</dispatcher> in the <servlet-mapping> element in DD. If you configure filter using above, the filter will invoke before the error page. In this filter you can forward the request to any of the page using RequestDispatcher.