JSF WABs using tag libraries from other bundles do not currently work out of the box.
See e.g. WarJSFPrimefacesIntegrationTest.
(The test misleadingly passes, but in fact it only checks that <panelGrid> gets rendered verbatim instead of being processed by PrimeFaces.)
In particular, the following JSF 2.1 and Servlet 3.0 requirements do not work at the moment:
Discovery of the ServletContainerInitializer of the JSF implementation
Discovery of META-INF/faces-config.xml of the taglib bundle
Discovery of META-INF/*.taglib.xml of the taglib bundle.
Loading static resources from META-INF/resources/ of the taglib bundle.