PowerMock is another mock framework that extends EasyMock and Mockito. With PowerMock you can easily remove unwanted behavior from a class, for example a static initializer. In your example you simply add the following annotations to your JUnit test case:
@RunWith(PowerMockRunner.class)
@SuppressStaticInitializationFor("some.package.ClassWithStaticInit")
PowerMock does not use a Java agent and therefore does not require modification of the JVM startup parameters. You simple add the jar file and the above annotations.