Refactoring a function with different signature
Simply use one method for all type of Exceptions. 

Make it public static and move into a utility class.

public static StringBuilder getMessageFromException(Exception e){...}


Why do you need overloaded methods for different type of Exceptions? 

User defined Exceptions are also subtype of Exception itself.



--EDIT--

create an interface for all your custom exceptions having  getFaultInfo() method.

interface MyFaultWS {} // marker interface
class FaultWS implements MyFaultWS {} // do it for both the packages

interface FaultInfoException {FaultWS getFaultInfo();}

// do it for both the packages
class FaultWS_Exception extends Exception implements FaultInfoException {

    @Override
    public FaultWS getFaultInfo() {
        return ...; // return your package specific exception
    }
} 


Finally use 

public static StringBuilder getMessageFromException(FaultInfoException e){...}