The keystore can be accessible by using the getCrypto() method on the KeyMaterialWssCrypto class. However, it's not really designed to be easily accessible through Groovy, so you may have to to a bit of boiler plate code to get it working.
There is also a test for soapUI cryptos (keystores) found here: svn://svn.eviware.com/soapui/branches/s ... oTest.java
that you might might useful.
Ref: http://www.soapui.org/apidocs/com/eviwa ... rypto.html
Hope this helps!