To get the Seam booking example run on WebSphere, you need to do quite a few tweaking. That includes to get around the J9 annotation processing bug (it does not ignore unknown annotations as the spec required), and various work arounds to make JSF RI and facelets run on WAS. None of them is really related to Seam itself ... Please see the websphere build for the JPA example for more details.
To answer your question, no, we do not have a set of regression tests that run against WAS.
We can try our best to help you make a successful WAS deployment. But for WAS internal issues, you have to call on IBM support ...
We are working on getting more information into the reference manual about deploying Seam onto different application servers (e.g. how the example is constructed, how to get a seam-gen'd up and running), tips and tricks like the annotations bug. I'm not sure of the roadmap atm for this (I think Glassfish will be done first, but is easier), but for the sort of content, take a look at the OC4J chapter in the trunk docs.