Tested with ICEfaces 4 trunk r43821.
After using the cloud push demo (simple push, priority push), then undeploying showcase, the following server errors are seen:
INFO: Waiting for 1 instance(s) to be deallocated for Servlet [Faces Servlet]
Dec 15, 2014 12:31:08 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/showcase] appears to have started a thread named [pool-1-thread-1] but has failed to stop it. This is very likely to create a memory leak.
Dec 15, 2014 12:31:08 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/showcase] appears to have started a thread named [pool-1-thread-2] but has failed to stop it. This is very likely to create a memory leak.
Dec 15, 2014 12:31:08 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/showcase] created a ThreadLocal with key of type [com.sun.faces.application.ApplicationAssociate$1] (value [com.sun.face
s.application.ApplicationAssociate$1@10d318f2]) and a value of type [com.sun.faces.application.ApplicationAssociate] (value [com.sun.faces.application
.ApplicationAssociate@130ac07f]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.

When using a few random demos in ACE showcase then undeploying .war file no server errors were seen.
When using the test application https://java.net/jira/browse/JAVASERVERFACES-3560 no server errors were seen.

Modified ICEpush bridge to shutdown blocking connection on beforeUnload. This aborts the blocking connection and unblocks the corresponding thread on the server.

Attaching test app for https://java.net/jira/browse/JAVASERVERFACES-3560 .

This issue seems to have been resolved by the fixes for ICE-10408 (rev. #43576).

There's still this SEVERE message shown when running with Mojarra:

Dec 2, 2014 11:23:33 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/showcase] created a ThreadLocal with key of type [com.sun.faces.application.ApplicationAssociate$1] (value [com.sun.faces.application.ApplicationAssociate$1@2ed7c530]) and a value of type [com.sun.faces.application.ApplicationAssociate] (value [com.sun.faces.application.ApplicationAssociate@57d2ea56]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak. 

After debugging it turns out that the ThreadLocal is created by Mojarra in com.sun.faces.application.ApplicationAssociate.

Tested with r43281 using Myfaces JSF. Please note that mobile-showcase was also tested on an android device during this deployment.

Server error seen when un-installing showcase application:
Oct 30, 2014 12:58:18 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/showcase] appears to have started a thread named [Timer-1] but has failed to stop it. This is very likely to create a memory leak.
Oct 30, 2014 12:58:18 PM org.apache.catalina.startup.ExpandWar deleteDir
SEVERE: [C:\Servers\apache-tomcat-7.0.42\work\Catalina\localhost\showcase] could not be completely deleted. The presence of the remaining files may cause problems
Oct 30, 2014 12:58:18 PM org.apache.catalina.startup.ExpandWar delete
SEVERE: [C:\Servers\apache-tomcat-7.0.42\work\Catalina\localhost\showcase] could not be completely deleted. The presence of the remaining files may cause problems