Release Project fails due to pom.xml not writable with perforce as SCM

All release steps from update-working-copy to map-development-versions work fine. The next phase ' rewrite-poms-for-release' fails because of read-only pom.xml.

this could be an issue with the scmUseEdit flag since perforce file are read-only by default.

see log output:
(I tried to fix alpha-2 by myself therfor log output is alpha2-SNAPSHOT, error reproduces with alpha-1, too)
[INFO] Updating local copy against the scm...
[INFO] Verifying that there are no local modifications...
[INFO] Checking dependencies and plugins for snapshots ...
[ERROR] org.apache.maven.shared.release.ReleaseExecutionException: Error writing POM: /home/drmtest/continuum-1.1-alpha-2-SNAPSHOT/continuum-webapp/src/main/webapp/WEB-INF/working-directory/1/pom.xml (Permission denied)
at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.writePom(AbstractRewritePomsPhase.java:659)
at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.writePom(AbstractRewritePomsPhase.java:604)
at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.transformProject(AbstractRewritePomsPhase.java:190)
at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.transform(AbstractRewritePomsPhase.java:115)
at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.execute(AbstractRewritePomsPhase.java:98)
at org.apache.maven.shared.release.DefaultReleaseManager.prepare(DefaultReleaseManager.java:194)
at org.apache.maven.shared.release.DefaultReleaseManager.prepareWithResult(DefaultReleaseManager.java:107)
at org.apache.maven.continuum.release.executors.PrepareReleaseTaskExecutor.execute(PrepareReleaseTaskExecutor.java:43)
at org.apache.maven.continuum.release.executors.AbstractReleaseTaskExecutor.executeTask(AbstractReleaseTaskExecutor.java:67)
at org.codehaus.plexus.taskqueue.execution.ThreadedTaskQueueExecutor$ExecutorRunnable$1.run(ThreadedTaskQueueExecutor.java:116)
at edu.emory.mathcs.backport.java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:442)
at edu.emory.mathcs.backport.java.util.concurrent.FutureTask.run(FutureTask.java:176)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:987)
at edu.emory.mathcs.backport.java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:528)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.io.FileNotFoundException: /home/drmtest/continuum-1.1-alpha-2-SNAPSHOT/continuum-webapp/src/main/webapp/WEB-INF/working-directory/1/pom.xml (Permission denied)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.<init>(FileOutputStream.java:179)
at java.io.FileOutputStream.<init>(FileOutputStream.java:131)
at java.io.FileWriter.<init>(FileWriter.java:73)
at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.writePom(AbstractRewritePomsPhase.java:640)
... 14 more